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Alphabetical Mineral Reference
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z  If you do not find the information you need here or in linked documents, try an alternative database gem database
Acanthite ... see argentite Accabar ... See Coral Colors: black Comments: can be dyed Achrite ... see Dioptase Achroite.... see colorless Tourmaline Actaeonella... fossil sea snail from Austria Acmite ... aegerine sodium iron silicate: (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6 Crystallography: monoclinic, prismatic (not over 1"); frequently massive in other rocks Colors: black, brown or green on thin edges Luster: glassy Hardness: 5 to 6 S.G.: 3.2 to 3.4 Cleavage: perfect Fracture: uneven Occurrence: common in U.S. Actinolite ... See also Tremolite, Nephrite calcium magnesium (iron) silicate: Ca2(Mg,Fe)5Si8O22(OH)2 Crystallography: Monoclinic; bladed crystals, usually elongated; fibrous, columnar aggregates, massive, granular, often twinned Colors: Pale to dark green, blackish green, black white (when it is free of iron it is Tremolite) Luster: Vitreous, at times dull glassy Hardness: 5.5 - 6 Specific gravity: 3 to 3.05 common (3.03-3.07) Cleavage: two directions good, fibrous, brittle, the compact variety is tough Refractive index: 1.619-1.644 Birefringence: .022-.026 Fracture: subconchoidal to uneven Cleavage: perfect prismatic Pleochroism : Yellow to dark green, transparent to opaque Occurrence: Contact metamorphic limestones and dolomites; magnesium-rich limestones and ultrabasic rocks; regionally metamorphosed rocks. Small, dark transparent crystals Crystal or stone size: to 10 cts Comments: Catseye, easy to cleave, hard to cut, poor jewelry stone, found in nephrite jade. Confused with: Wollastonite which is commonly fluorescent before heating, and dissolves in hydrochloric acid. Scapolite melts more easily and is or becomes on heating, fluorescent in long wave UV. Epidote melts readily to black slag Adamantine spar ... see Corundum Adamite zinc arsenate: Zn2(AsO4)(OH) Crystallography: orthorhombic, drusy crust of short prismatic or horizontally elongated crystals Colors: Colorless, pale green, yellowish green, yellow shades, bluish green, green, rose, violet, color zoning Luster: Vitreous Hardness:3.5 Specific gravity: 4.32-4.48 Cleavage: Good in one direction,fracture conchoidal to uneven Refractive index: 1.708-1.773 Birefringence: .031-.05 Pleochroism: Colorless, blue-green, yellow-green, pale rose, pale purple, pink Occurrence: Secondary mineral in the oxidized zone of ore deposits Crystal or stone size: To 3 cts Comments: Rare (crystal), poor jewelry material, but a collector's item; brilliant fluorescence in light yellow to white when free of iron, green is non fluorescent and can be distinguished from smithsonite by the lack of CO2 bubbles in solution in HCl Adularia ... See Feldspar Aegirine ... See Acmite African Jade ... Massive green Grossular Garnet Agalmatolite ... See Pyrophyllite, Pinite, Talc Agate ... See quartz .. Chalcedony .. Banded Quartz Agatized Wood...See Quartz, Fossilized Wood, Chalcedony Agmatite ... Found in migmatites, an ultrametamorphic rock Color: dark with lighter veins Comments: contains: quartz, feldspar; used as building stone. Found in the Black Forest (Germany) Alabaster ... See Calcite, Gypsum Albite ... See Plagioclase Feldspars Alexandrite ... see Crysoberyl Allanite ... orthite (Ca,Ce,La,Na)2(Al,Fe,Be,Mn,Mg)3(SiO4)3(OH) Crystal: monoclinic, prismatic Color: black to dark brown Luster: pitchy or resinous Hardness: 5.5 - 6 SG: 2.7 - 4.2 Fracture: subconchoidal to uneven Cleavage: poor Environment: pegmatites, as a minor mineral in igneous rocks Comments: fuses quickly (with bubbling) to a dull black magnetic glass; radioactive Allemontite .. See Arsenic Almandine ... See Garnet Colors: purplish red Hardness: 7.5 SG: 3.9 to 4.2 RI: 1.76 to 1.81 Comments: colored with iron Almandite ... almandine ... see Garnet Alunite ... alumstone hydrous sulfate of aluminum and potassium: KAl3(SO4)2(OH)6 Crystallography: Hexagonal, usually massive crystals are rare Colors: white, gray, pink Luster: vitreous to pearly,translucent to transparent Hardness: 3.5 - 4 Specific gravity: 2.6 - 2.9 Fracture: flat conchoidal to uneven, brittle Cleavage: basal, brittle, conchoidal to uneven Occurrence: altered orthoclase feldspar rich rocks, massive alunite Crystal or stone size: massive crystals are rare Comments: sometimes florescent orange in LW UV; closely resembles limestone and dolomite; a mountain of alunite is in Marysvale Utah Amazon Jade ..amazonstone.. see Microcline (Feldspar) Amazonite ... See Feldspar Amber... See also Succinite Amblygonite ... Also Montebrasite, Natromontebrasite LiAl(PO4)(F,OH) Crystallography: triclinic, pinacoidal Colors: colorless, yellow, white, light gray green, lilac, gray blue Luster: glassy Fracture: uneven to subconchoidal Hardness: 5.5 to 6 Specific gravity: 3 to 3.1 Cleavage: perfect Comments: most stones come from pegmatite dikes in Brazil, Main and Burma Lithia; fluorescent in LW weak orange Amethyst ... see Quartz Amianthus ... see Tremolite, Actinolite Ammonite ... shell replaced by pyrite Amphibolite ... see hornblende .. a rock Analcime .. Also Pollucite, Zeolite group, Analcite NaAlSi2O6.H2O Crystallography: cubic, tetragonal trisoctahedron (trapezohedron) transparent to translucent Colors: colorless, white, greenish, reddish Luster: glassy Hardness: 5 to 5.5 Fracture: subconchoidal Specific gravity: 2.3 Cleavage: traces of cubic Comments: after heating to the point of melt and then cooling it florescences yellow green Anatase ... TiO2 ... titanium oxide crystallography: tetragonal Colors: blue, light yellow to brown Luster: adamantine to submetallic Hardness: 5.5 to 6 S.G.: 3.8 to 3.9 Cleavage: perfect basal Fracture: subconchoidal Comments: collector crystal, found in Alpine regions; NC,MA,CO. & France Andalusite ...See Kyanite, Sillimanite.^M Varieties: Chiastolite, Viridine Al2SiO5 Crystallography: orthorhombic Colors: green, greenish brown w/ reddish tints chiastolite is impure variety showing gray cross on black or gray ground. Hardness: 7.5 Specific gravity: 3.15 Cleavage: perfect Refractive index: mean 1.64 v .01 Pleochroism: striking in one direction Comments: often confused with tourmaline, but has lower DR & higher SG Andesite ... igneous rock Essentials: plagioclase, anorthite, biotite Accessories: magnetite, ilmenite, quartz, hornblende pyroxene, glass Accidentals: olivine, orthoclase, anorthoclase Andradine ...see garnet .. andradite Crystallography: Isometric Colors : Demantoid is green, Topazolite is yellow, Leuco is colorless Hardness: 6.5 Specific gravity: 3.85 Refractive index: 1.89 Comments: very high dispersion not usually suitable for jewelry, varieties as demantoid, melanite and topazolite usually have gem qualities. Anglesite ... lead sulfate ... PbSO4 Crystal system: Orthorhombic Colors: colorless to white, gray, green, brown, black. Hardness: 2.75 to 3 very soft Specific gravity: 6.3 Comments: alteration of galena in oxidation areas of lead deposits. Faceted stones from Morocco (colorless 19 ct.) were sold for $50.00 per.ct. (1994) Anhydrite ... CaSO4 Crystallography: orthorhombic Colors: colorless, bluish, red - violet Hardness: 3.5 Specific gravity: 2.9 - 2.99 Cleavage: 3 good Fracture: uneven to splintery Environment: sedimentary beds, gangue in ore veins and in traprock zeolite occurrences. Crystals are collector items. Sometimes fluorescent. Easily altered to gypsum through hydration. Annabergite ... hydrated nickel arsenate (Ni,Co)3(AsO4)2.8H2O Crystal system: monoclinic Color: white to green Luster: silky to glassy SG: 3.1 Hardness: 2.5 - 3.0 Comments: forms as crust on nickel minerals, sometimes replacing the mineral completely; Best place to see in the US is in Humboldt, CO. Anorthite ... a variety of feldspar ...see labradorite, oligoclase sodium calcium alum. silicate Color: colorless, white, yellowish, green, pink, to reddish SG: 2.62 - 2.76 Comments: can be found in triclinic crystals or in massive form Anorthosite ... intrusive igneous rock Color: dark gray Comments: contains plagioclase, anorthite, labradorite - bytownite, orthopyroxene, with some olivine, magnetite, ilmenite, apatite, chromite, and sulfide. It also rarely contains biotite, hornblende and cordierite. Can be found in San Diego,CA. Anthophyllite ...(Mg,Fe)7Si8O22(OH)2... hydrous magnesium iron silicate Crystal sys.: orthorhombic Color: gray, light green, light brown SG: 2.8 - 3.2 Hardness: 5.5 - 6 Cleavage: prismatic Comments: modification of olivine through hydration crystals are rare. Franklin Co. N.C. Anthracite ... bituminous coal ... jet Crystallography: organic Colors: black Luster: high Hardness: 2.5 - 4 Specific gravity: 1.3 - 1.35 Cleavage: none Refractive index: 1.64 - 1.68 Pleochroism: none Crystal or stone size: massive Occurrence: world wide: Spain, France, U.S. Comments: when rubbed can become electrically charged. Antigorite ... see serpentine Antimony ... see arsenic Antlerite...Cu3(SO4)(OH)4...Sulfate of copper Crystal: Rhombic bipyramidal Color: bright to dark green Luster: glassy Hardness: 3.5 - 4 SG: 3.9 Fracture: uneven Cleavage: pinacoidal perfect side, poor front Comments: Like brochantite is a mineral of the oxidized zones of copper deposits in siliceous rocks that cannot supply an abundance of the CO2 required for the formation of the carbonate group of copper minerals. Apache Tears ... see obsidian Comments: round or simi round, marble like, dark blackish green. Apatite Crystallography: hexagonal Colors: yellow, blue, green, violet Hardness: 5 Specific gravity: 3.18 to 3.21 Cleavage: none Refractive index: avg. 1.638 v .003 Occurrence: blue from Burma, strong dichroism Comments: yellow shows rare earth absorption bands (584 nm.); very low DR & higher SG distinguish it from danburite Aplite ... see orthoclase Apophyllite Crystallography: tetragonal Colors: pink Hardness: 4.5 to 5 Specific gravity: 2.3 to 2.5 Refractive index: avg. 1.536 v. .001 Comments: hydrated potassium-calcium fluosilicate rarely cut, a collector gem. Aquamarine ... see Beryl Refractive index: 1.75 +/- .006 Aragonite Crystallography: orthorhombic Colors: colorless various tints Luster: vitreous Hardness: 3.5 - 4 Specific gravity: 2.94 Refractive index: 1.53 - 1.685 Occurrence: can form crystals large enough to cut Comments: is the "orient" produced by overlapping of platelets near a pearls surface (pearl RI is 1.52 - 1.69). Arenite ... clastic sedimentary rock Color: variable, from white to gray, yellow, green, red to brown. Comments: composed of quartz sand with other minerals as color: feldspar, mica, calcite, zircon, apatite, olivine, monazite, pyrite, magnetite, gypsum, glauconite. Arfvedsonite ... hydrous sodium iron mag. alum. silicate Crystal Sys.: monoclinic Color: black to greenish black SG: 3.5 Hardness: 5 Comments: found in alkaline plutocic rocks rich in iron and in rare metamorphic schist. Argentite ... acanthite Crystallography: cubic Colors: black, gray Luster: metallic Hardness: 2 to 2.5 Specific gravity: 7.3 Cleavage: poor Fracture: subconchoidal Comments: Argillite ... sedimentary rock Color: light to dark gray to black Comments: fine grain, mixture of clay minerals with quartz, feldspar, mica, some carbon, iron oxides, gypsum, & pyrite. Classic marine & glacial deposits. Arkansas diamond ... see clear quartz Comments: so named because some of the best come from Arkansas Arkose ... sedimentary rock Color: gray, pink or reddish Comments: coarse grains of feldspar, some quartz, biotite, mica and other minerals derived from igneous and lithic fragments, the binding agent may be silicate, calcitic, or limonitic. Arsenoferrite ... see skutterudite Arsenic ... Crystal system: hexagonal (rare) Color: black w/ white incrustations SG: 5.4 - 5.9 Hardness: 3.5 Comments: hydrothermal veins; associated with silver, nickel, cobalt. Arsenopyrite ... iron arsenic sulfide Color: silver to whitish gray with pink tints SG: 5.9 - 6.2 Hardness: 5.5 - 6 Asbestos .. see tremolite , actinolite , serpentine Comments: asbestos is a finely fibrous serpentine; crysotile is a coarser fibrous type. Artinite ... hydrated magnesium carbonate Crystal system: monoclinic Color: white to gray SG: 2.03 Hardness: 2 Astrophyllite ... hydrous potassium iron titanium silicate Color: golden yellow to yellow brown SG: 3.3 - 3.4 Hardness: 3.5 - 4.5 Atacamite ... hydrous copper chloride Crystal sys. orthorhombic Color: green SG: 3.76 Hardness: 3 - 3.5 Augelite ... Colors: colorless to brownish Hardness: 4 Specific gravity: 2.7 Refractive index: 1.574 to 1.588 Comments: aluminum phosphate Augite ... calcium magnesium iron aluminum silicate..(see pyroxene) Aurichalcite ... hydrous zinc copper carbonate Color: light blue SG: 4.2 Hardness: 2 - 2.5 Austinite .. Australite .. moldavite from Australia Colors: bottle green to brown green Hardness: 5.5 Specific gravity: 2.32 - 2.38 Cleavage: none Refractive index: 1.48 - 1.5 Comments: tektite formed from rock which has melted after being hit by a meteorite Autunite ... hydrated copper uranium phosphate Crystal sys. tetragonal Color: greenish yellow SG: 3.2 Hardness: 2 - 2.5 Aventurine .. see quartz Axinite Crystallography: triclinic Colors: blue, clove brown, violet Fracture: conchoidal, brittle Hardness: 7 Specific gravity : avg. 3.28 Cleavage: perfect Refractive index: 1.685 + - .011 Pleochroism: strong; olive green, red - brown, yellow - brown Occurrence: in bladed crystals,U.S.,France,Mexico Comments: occurs in bladed crystals Azurite Babingtonite ... Hydrous calcium iron manganese silicate Crystal sys: triclinic Color: black or blue to brown when altered SG: 3.4 Hardness: 5.5 - 6 Bakerite ... see howlite Balas ruby ... see spinel Banded agate...see quartz..chalcedony Barite ... Crystallography: orthorhombic Colors: colorless, yellow, red, green, black Hardness: 2.5 - 3.5 Specific gravity: 4.48 Occurrence: med. to low temp. hydrothermal veins assoc. with lead, silver, antimony Also deposits in hot springs Crystal or stone size: up to 3.3 ft. Comments: sometimes fluorescent Basalt ... A basic igneous rock Basalt is formed from a lava that solidifies to a fine grained black rock composed of microscopic grains of calcium sodium (plagioclase) feldspar, pyroxene, and olivine, but with no quartz. Basanite ... see quartz .. also touchstone Colors: velvet black Bastite ... bastinite ... hureaulite Hydrous manganese phosphate Crystal sys: monoclinic Color: pink, gray, yellow, reddish brown SG: 3.2 Hardness: 3.5 Comments: pronounced {hoo-ray'o-lite} Bauxite ... {bawks'-yt} Crystallography: none, an aggregate Colors: reddish to brown, white to yellowish Luster: vitreous to pearly Hardness: 2.5 - 3 Specific gravity: 2.3 - 2.7 Cleavage: perfect Occurrence: sedimentary ; Surinam, Jamaica, US, world wide. Comments Becquerelite ... see gemmite Benitoite Crystallography: Hexagonal Colors: sapphire blue to colorless Hardness: 6.5 Specific gravity: 3.67 Refractive index: 1.78 + - .047 Comments: Rare stone from San Benito Co. Cal. strong DR and high dispersion Bertrandite Crystallography: orthorhombic Colors: colorless to pale yellow Luster: vitreous Hardness: 6 -7 Specific gravity: 2.6 Cleavage: excellent prismatic Occurrence : pegmatites US Crystal or stone size: to 1 cm Comments: of interest to mineralogists & collectors Beryl {bair'-ul}...see also aquamarine , emerald, heliodor, morganite Colors: colorless, gold, yellow-green, yellow, pink, , green (emerald), pale blue to blue green (Aquamarine), golden to yellow (heliodor), pink (Morganite) Beryllonite ... NaBePO4 ... sodium beryllium phosphate Crystal: monoclinic Hardness: 5.5 - 6 Luster: glassy SG: 2.8 Fracture: conchoidal Cleavage: good basal, brittle, transparent to translucent Comments: Fuses with difficulty to a cloudy glass, wet with sulfuric acid and the powdered mineral froths. coloring flame is yellow. Betafite ... hydrous uranium titanium niobium oxide Crystal sys: isometric Color: black, sometimes coated w/greenish brown or yellow surface alteration SG: 3.7 - 5 Hardness: 5 Comments: occurs in pegmatites, ore of uranium thorium, niobium. Bindheimite ... see boulangerite Binnite ... see tetrahedrite tennantite Biotite ... see mica Bismuth ... {biz'-muhth} Crystal sys: hexagonal Color: A tarnished rose pink SG: 9.7 - 9.8 Hardness: 2 - 2.5 Comments Bismuthinite ... bismutite Crystal sys: orthorhombic Color: gray SG: 6.4 - 6.5 Hardness: 2 Comments: rare free growing needles, first named cannizarite because of unbismuthlike needles. Found in NY,CO,Brazil Bixbite ... collector mineral (bixbyite) Crystal system: cubic Color: Black, metallic H: 6 - 6.5 SG: 4.9 - 5.1 Brittle Blend ... sphalrite Crystallography: cubic Colors: brown, yellow, orange, black, transparent to opaque green Hardness: 3.5 Specific gravity: 3.09 Cleavage: perfect dodecahedral Refractive index: avg. 2.37 Comments: good color luster and fire but too soft to take a high polish Bloodstone...see chalcedony (quartz) Colors : usually green with red spots Luster: dull to waxy Hardness: 7 or less Specific gravity: 2.55 to 2.62 Cleavage: none Refractive index: 1.535 to 1.539 Boehmite ... see bauxite Boleite ... hydrated lead copper chloride Crystal sys: tetragonal Color: dark blue SG: 5.05 Hardness: 3.5 Bonamite ... see smithsonite H: 5 SG: 4.35 RI: 1.62 Borax {bohr'-ahn} boron, hydrated sodium borate, borax acid Crystal sys: monoclinic Color:colorless to white with yellow or blue tint SG: 1.74 Hardness: 2 - 2.5 Comments Bornite ... {bohr'-nyt}...copper iron sulfide Crystallography: isometric Colors: reddish brown, showing purple tarnish Hardness: 3 Specific gravity: 5 - 5.7 Comments Boulangerite ... lead antimony sulfide Crystallography: orthorhombic Colors: dark gray to black Luster: metallic Hardness: 2.5 - 3 Specific gravity: 5.7 - 5.9 Occurrence: hydrothermal veins, found with galena,silver, antimony deposits. Crystal or stone size: stubby or tubular prismatic crystals. Comments: dissolves in nitric acid Bort ... see diamond ... bortz Comments: diamond unsuitable for gemstones, used in cutting and polishing. Bournonite ... lead copper antimony sulfide Crystallography: orthorhombic Colors: dark gray to black Luster: metallic Hardness:2.5 - 3 Specific gravity: 5.7 - 5.9 Cleavage: good Comments: used as an ore of lead and copper Bowenite SG:2.59 Avg.RI: 1.55 H: 5.5 Brazilianite Crystallography: monoclinic Colors: colorless to greenish yellow to transparent or translucent Hardness: 5.5 Specific gravity: 2.99 Refractive index: avg. 1.612 v. .021 Occurrence : Minas Gerais, & New Hampshire Breccia ... {brech'-ee-uh} sedimentary rock Crystallography : none Colors : variable Luster : can be polished like marble Hardness: variable Occurrence: found in limestone and dolomite Crystal or stone size: massive Comments Breithauptite ... see niccolite Brochantite ... hydrous copper sulfate Crystallography: monoclinic Colors : bright green Hardness: 3.5- 4 Specific gravity: 3.97 Cleavage: perfect Comments: ore of copper Bromyrite ... bromargyrite Crystal system: cubic Colors: colorless, greenish gray, gray to violet brown Adamantine luster H: 1 - 1.5 SG: 5.5 Bronzite ... see enstatite ... hypersthene Crystallography: orthorhombic Colors : greenish brown or blackish Luster: submetallic Hardness: 5 Specific gravity: 3.2 - 3.5 Brookite ... titanium oxide Crystallography: orthorhombic Colors: brown to black sometimes banded Luster: adamantine Hardness: 5.5 - 6 Specific gravity: 4.1 Cleavage: imperfect Comments: ore of titanium Brownspar ... see calcite Brucite ... magnesium hydroxide Crystallography: hexagonal Colors: colorless, green, blue, pinkish yellow, brown Luster: pearly Hardness: 2.5 Specific gravity: 2.4 Occurrence: fracture planes in serpentinized peridotites in asbestos mines Comments: used for magnesia refractories and a source of metallic magnesium. Buergerite ... see tourmaline Bytownite ... see plagioclase feldspar Cabrerite ... see annabergite Calamine ... hemimorphite ... smithsonite hydrated zinc silicate ... ore of zinc Calaverite ... AuTe2 ... see sylvanite (Au,Ag)Te2 Calciphyre ... calci - silicate rocks Color: yellow brown w/pink/light green/white & dark red zones Comments Calcite ... calcium carbonate Crystallography: hexagonal Colors: whitish, red, pink, yellow, blue Luster: iridescent or pearly Hardness: 3 Specific gravity: 2.71 Comments: some are fluorescent in UV, red, yellow pink blue Caledonite ... Cu2Pb5(SO4)3(CO3)(OH)6... carbonate sulfate of lead and copper Color: light blue to light blue green Crystal: orthorhombic Luster: resinous Hardness: 2.5 - 3 SG: 5.8 Fracture: uneven Cleavage: 1 good, 1 poor, brittle, translucent Comments: rare Californite ... see vesuvianite... hydrous calcium magnesium aluminum silicate. an aggregate combo of idocrase and grossular garnet Color: apple green SG: 3.3 Avg.RI: 1.7 H: 5.5 to 7.5 Comments: $450.00 per ct. when cut from crystal. Calomel ... HgCl ... Crystal: tetragonal, (minute) Color: gray to yellowish Luster: adamantine Hardness: 1 - 2 SG: 6.5 Fracture: conchoidal Cleavage: 2 , 1 good, sectile, translucent Comments: Fluorescent red Campylite ... see mimetite Cancrinite ... tectosilicate Crystallography: hexagonal Colors: colorless, yellow, white, reddish, violet Hardness: 5 - 6 Specific gravity: 2.4 - 2.5 Comments: collector item Cannizarite ... see bismuthinite Carbonatite ... igneous rock Color: gray to yellowish Comments: South Africa; used in the extraction of minerals and rare elements Carnallite ... hydrated potassium magnesium chloride Crystal sys: orthorhombic Color: colorless to reddish pink SG: 1.6 Hardness: 2.5 Comments: potassium fertilizer Carnelian ... see chalcedony Colors: red to orange Occurrence: looks like jade and fire opal Carnotite ... hydrated potassium uranium vanadate Crystallography: monoclinic Colors: canary yellow Hardness: very soft, clumpy powder Specific gravity: 4.7 - 5 Cleavage: perfect Occurrence: very common in desert areas of U.S. Crystal or stone size: crystals are rare Comments: ore of uranium and vanadium Cassiterite ... tin oxide Crystallography: tetragonal Colors : colorless to dark brown Luster: adamantine Hardness: 6.5 Specific gravity: 6.95 to 7 Cleavage: imperfect conchoidal Refractive index: avg. 2.045 v. .096 Comments: high luster and dispersion, has been used as a diamond substitute Celestite ... celestine ... strontium sulfate Colors: colorless, white, red brown, orange, light blue. Luster: glassy H: 3 - 3.5 SG:3.9 - 4 Comments: sometimes fluorescent, geodes from Madagascar can be lined with these blue crystals. Cerargyrite .. bromyrite .. secondary silver ore Color: greenish gray to gray H: 1 - 1.5 SG: 5.5 Comments: composed of 60 to 75 % silver chloride yellow crystals were found in New South Wales, which darken to gray in sunlight. Cerussite ... lead carbonate Crystallography: orthorhombic Colors: colorless, white Luster: Adamantine Hardness: 3 - 3.5 Specific gravity: 6.5 Occurrence: Namibia, new Mexico, Rhodesia USSR, Germany, Colorado Crystal or stone size: some crystals are very large, 50/60 cts, @ $100 per ct. Comments: ore for lead, bright green fluorescence Cervantite ... stibnite .. antimony sulfide Crystal sys: orthorhombic Color: red (kermesite), yellow SG: 4.6 -4.7 Hardness: 2 Comments: ore of antimony Chabazite ... hydrated calcium aluminum silicate Crystallography: hexagonal Colors: colorless, white, greenish, reddish Luster: vitreous Hardness: 4 - 5 Specific gravity: 2.05 Cleavage: good rhombohedral Occurrence: world wide, intrusive igneous rocks Comments: collector item Chalcanthite ... hydrated copper sulfate ore of copper Crystal sys: triclinic Color: colorless SG: 2.3 Hardness: 2.5 Comments: major ore of copper in Chile Chalcedony types Crystallography: fine grained quartz Colors: all Luster: waxy Hardness: 6.5 - 7 Specific gravity: 2.6 + - .05 Cleavage: none Refractive index: 1.535 - 1.539 Crystal or stone size: can be massive Comments: this is a very general name for all fine grained quartz.look up types under its own name Chalcocite ... tobernite ... copper sulfide Crystal sys; orthorhombic Color: dull gray, surface altered to black/green SG: 5.5 - 5.8 Hardness: 2.5 - 3 Comments: ore of copper Chalcopyrite {kal-koh-py'-rite} copper iron sulfide Crystallography: tetragonal Colors: brassy yellow Luster: metallic Hardness: 3.5 - 4 Specific gravity: 4.2 - 4.3 Cleavage: none Occurrence: world wide Crystal or stone size: massive Comments Chalcosine ... see chalcocite Chalcotrickite ... cuprite ... copper oxide Crystallography: isometric Colors: ruby red Luster: adamantine Hardness: 3.5 - 4 Specific gravity: 5.8 - 6.2 Crystal or stone size: rare crystals have been cut as gems Comments: ore of copper Chert ... see quartz Chessylite ... see azurite Chiastolite ... see andalusite Childrenite ...(Fe,Mn)Al(PO4)(OH)2.H2O... Hydrous iron and manganese aluminum phosphate Crystal: orthorhmbic Color: pink to light brown, gray to black Luster: glassy Hardness: 4.5 SG: 3.06 - 3.25 Fracture: conchoidal Cleavage: front and side pinacoid, brittle Chlorargyrite ... silver chloride Crystal sys: isometric Color: gray, tarnish to greenish/purple/brown SG: 5.5 - 5.6 Hardness: 1 - 1.5 Comments: silver ore, hard to find Chloritoid ... hydrous iron magnesium aluminum silicate Crystallography: monoclinic and triclinic Colors: yellow - green to black Luster: vitreous to pearly Hardness: 6.5 Specific gravity: 3.51 - 3.8 Occurrence: found in low grade metamorphic rocks rich in aluminum, iron and manganese Crystal or stone size: in contact with marbles corundum and quartz. Comments: collector item Chondrodite Crystal system: monoclinic Colors: yellow to dark reddish brown Luster: resinous Hardness: 6 - 6.5 SG: 3.14 Cleavage: poor Comments: fine crystals are found in Sweden a collector item. Chromite ... iron chromium oxide Crystallography: isometric Colors: black Luster: submetallic Hardness: 5.5 Specific gravity: 4.5 - 4.8 Cleavage: none Crystal or stone size: massive Comments: ore of chromium, a chromium and iron oxide, in the SPINEL group of minerals. Metallic black chromite generally is associated with serpentinites, peridotites, and related rocks. It forms large, irregular, compact masses in ore deposits and also occurs in stony iron meteorites. Chrysoberyl...{kris'-uh-bair-ul}... cymophane, alexandrite, cats eye Crystallography: orthorhombic Colors: green/red (alexandrite), greenish or brownish yellow to translucent and chatoyant (cat eye) colorless to brown Hardness: 8.5 Specific gravity: 3.71 - 3.73 Cleavage: distinct in two directions Refractive index: avg. 1.75 v. .009 Pleochroism: strong in alexandrite Occurrence: Siberia, Brazil Crystal or stone size: Alexandrite in Siberia less than 1 ct. Brazilian stones are larger. Comments Crysocolla ... see chalcedony SG: 2.1 Avg. RI: 1.5 H: 2 Chrysolite ... see olivine Chrysotile ... see serpentine ... asbestos Chrysoprase...see chalcedony Color : yellowish green SG: 2.6 Avg.RI: 1.53 H: 7 Comments: confused with jade, poor emerald, serpentine Cinnabar {sin'-uh-bar} cinnabarite, mercury sulfide Crystallography: hexagonal Colors: red, pink Hardness: 2 - 2.5 Specific gravity: 8.1 Cleavage: perfect low temp. hydrothermal deposits Comments Citrine ... see quartz Clinochlore...see chlorite...hydrous magnesium iron - aluminium silicate... see penninite Crystallography: monoclinic Colors: blue green, yellow, rare white Luster: pearly Hardness: 2 - 2.5 Specific gravity: 2.6 - 2.8 Cleavage: perfect basal Comments: of interest to collectors Clinoenstatite...see enstatite, hypersthene Clinozoisite...Hydrous calcium aluminum silicate Crystal sys: monoclinic Color: gray, pale green, pink SG: 3.3 - 3.5 Hardness: 6.5 Comments: Elongated prismatic crystals, poorly terminated Cobaltite ... cobalt arsenic sulfate Crystallography: orthorhombic Colors: gray, violet to purple tint Luster: metallic Hardness: 5.5 Specific gravity: 6.3 Cleavage: perfect Crystal or stone size: 1" Comments: CoAsS, is the chief ore mineral of cobalt, containing up to 35 percent of the element. A secondary source of arsenic, cobaltite contains up to 10 percent iron and some nickel as impurities. The cubic crystals (ISOMETRIC SYSTEM) are silver white. Luster metallic, streak grayish black. It occurs with other cobalt and nickel minerals and, more commonly, in contact metamorphic zones. Colemanite ... hydrated calcium borate Color: white, tinted red to pink by impurities SG: 2.4 Hardness: 4 - 4.5 Comments: A main ore of boron Columbite - tantalite group,iron maganese niobium tantalum oxide Crystal System: orthorhombic Colors: black SG: 5.3 - 8.1 Comments: Ore of niobium and tantalum, used in stainless steel Conichalcite... hydrous calcium copper arsenate Crystal sys: Orthorhombic Color: shades of green SG: 4.3 Hardness: 4.5 Comments: A secondary mineral occurring in the oxidation of copper Copiapite ... hydrated iron sulfate Crystal sys: triclinic Color: olive green to yellow or orange SG: 2.08 - 2.17 Hardness: 2.5 Comments: A secondary mineral that occurs in the upper portions of sulfide deposits, dissolves easily in water. Copper Crystal sys: isometric Color: copper color tinted with green or blackish film SG: 8.93 Hardness: 2.5 - 3 Comments Coral ... White, pink, black, red Crystallography: none, organic Colors: red, pink, black, white, can be dyed Hardness: 3.5 - 4 Specific gravity: 2.12 Refractive index: 1.55 - 1.57 Occurrence: warm seas Comments: Coral has a tree-like form, and a radial fibrous cross section. White is the most common, coral occurs in warm tropical waters having a temp. above 68 F. The Romans believed it had strong healing powers. Cordierite...{kohr'-dee-uh-ryt}... magnesium aluminum silicate...iolite Crystallography: orthorhombic Colors: gray, blue, black, purple Luster: glassy Hardness: 7 - 7.5 Specific gravity: 2.61 - 2.66 Cleavage: poor, gem v. distinct Refractive index: 1.542 - 1.551 Comments Corundum{kuh-ruhm'-duhm}...sapphire...ruby Crystallography: Hexagonal Colors: red = ruby, all other colors = sapphire red - orange = padparadsha sapphire Hardness: 9 Specific gravity: 3.99 Cleavage: false ,which may be well developed Refractive index: avg. 1.762 to 1.77 v. .008 Comments Covellite ... covelline ... copper sulfide Crystal sys: hexagonal Color: indigo blue SG: 4.59 - 4.76 Hardness: 1.5 - 2 Comments: ore of copper Cristobalite ... silicon oxide Color: colorless to white or gray SG: 2.3 Hardness: 7 Comments: only of interest to collectors Crocidolite SG: 2.66 Avg.RI: 1.54 H: 7 Cryolite ... sodium aluminum fluoride Crystallography: monoclinic Colors: white , colorless Luster: vitreous or pearly Hardness: 2.5 Specific gravity: 2.95 - 3 Comments: used in pottery glazes and glass Cubic Zirconia...man made Colors: all Hardness: 8.5 Specific gravity: 5.8 + - .2 Refractive index: 2.15 + - .03 Occurrence: man made Crystal or stone size: up to 2" usual 1" or less Comments: usually orange or yellow fluor. under UV. Cummingtonite...hydrous magnesium silicate Crystal sys: monoclinic Color: brown SG: 3.1 - 3.7 Hardness: 5 - 6 Comments: of interest to collectors Cuprite...{koop'-ryt}... copper oxide Crystallography: isometric Colors: dark ruby red Luster:adamantine Hardness: 3.5 - 4 Specific gravity: 5.8 - 6.2 Comments: Cuprite, copper oxide is a common and widespread ore mineral formed by oxidation of sulfide minerals in the upper zones of copper veins. It forms octahedral crystals (ISOMETRIC SYSTEM) and granular masses that are various shades of red; parallel, elongated ruby -red needles are called chalcotrichite, and brick - red earthy masses are called tile ore. Cuprite's streak is bright brownish red. Some crystals are cut as gems @ $200.00 per ct. Cyanite...see kyanite Color: blue SG: 3.67 Hardness: 6-7 one direction/4-5 in the other Comments: sometimes used as gemstone, also used in the manufacture of porcelain. Cyanotrichite ... hydrated copper aluminum sulfate Color: blue SG: 2.75 Hardness: 1 Comments: rare alteration in copper deposits. Dacite ... extrusive igneous rock Colors: medium gray Occurrence: lava flows, dikes Crystal or stone size: massive Comments: no commercial value Danburite ... calcium borosilicate Crystallography: orthorhombic Colors: pale yellow, colorless Luster: vitreous Hardness: 7 Specific gravity: 3 Cleavage: poor Refractive index: avg. 1.633 v. .006 Occurrence: Burma Crystal or stone size: Comments: Lower SG / RI distinguish it from topaz. Datolite...hydrous calcium borosilicate Crystallography: monoclinic Colors: colorless to yellow to brown, cloudy nodules in various colors. Luster: vitreous Hardness: 5 Specific gravity: 2.99 Refractive index: avg. 1.648 v. .044 Crystal or stone size: to 5 cts. cab.cut @ 250 pc. Comments: collector stone, ore of boron Demantoid....garnet...andradite Crystallography: Colors: green Hardness: 6.5 - 7 Specific gravity: 3.85 Refractive index: 1.875 -1.89 Comments: high dispersion, horse tail inclusions Dendrite ... pyrolusite ...maganese oxide Crystallography: tetragonal Colors : black Luster: submetallic Hardness: 6 - 6.5 Specific gravity: 4.7 - 5 Comments: can be tree like inclusions Descloizite ... hydrous lead zinc vanadate Crystallography: orthorhombic Colors: orange to reddish brown Luster: greasy Hardness: 3.5 Specific gravity: 5.5 - 6.2 Occurrence: massive Comments: rare ore of vanadium Diabase ... {dy'-uh-bays} igneous rock Comments Diamond...(boart, carbonado are industrial types) Occurrence Comments Diaspore ... see bauxite Diopside... pyroxene group Crystallography: monoclinic Colors : pale to dark green Hardness: 5 Specific gravity: 3.29 Refractive index: avg. 1.69 v. .03 Chatoyant: some 4 ray stars Comments : Different shade of green from peridot and higher RI lower DR. Enstatite has lower DR Dioptase ... hydrous copper silicate Crystallography: hexagonal Colors: green Hardness: 5 Specific gravity: 3.3 Cleavage: perfect Comments: used as cabs in jewelry, rare faceted blue green stones up to 2 cts. @ 500 a piece Diorite {dy'-uh-ryt} intrusive igneous rock Colors: dark gray Comments Dolomite {doh'-luh-myt} calcium magnesium carbonate Crystallography: hexagonal Colors: colorless, white, pink, yellowish Luster: vitreous Hardness: 3.5 - 4 Specific gravity: 2.85 - 2.95 Comments Dumortierite ... aluminum borosilicate Crystallography: orthorhombic Colors: blue, violet reddish brown Luster: vitreous Hardness: 7 Specific gravity: 3.45 Occurrence: world wide Comments: used in manufacture of aluminums refractories Dunite {doo'-nyt} intrusive igneous rock...see olivine Colors: light green Comments Eclogite {ek'-luh-jite}... metamorphic rock Color: white with red Comments Ekanite Colors: green Luster: glassy Hardness: 5 - 6.5 Specific gravity: 3.28 Refractive index: 1.597 Occurrence: Ceylon Crystal or stone size: 1 to 3 cts. Comments: radioactive, collector gem, @ 150 per ct. Embrechite ... Migmatite .. ultrametamorphic rock Color: white w/black Comments: essentials: quartz, potassic feldspar oligoclase, biotite sometimes: zircon apatite, magnetite. Rare: muscovite, cordierite, sillimanite, garnet Embolite ... see cerargyrite .. bromyrite Emerald...see beryl Crystal or stone size: usually less than 2 ct. in gem quality. Comments Enargite {en-ar'-jite}.. copper arsenic sulfide Crystal sys: orthorhombic Color:gray to black SG: 4.4 - 4.5 Hardness: 3 Comments: Enargite, a fairly rare copper arsenic sulfide mineral, is an important ore of copper and arsenic in the few places where it is abundant, such as Bor, Yugoslavia and Butte, Mont. Enargite forms metallic black, tabular, or prismatic crystals and granular, cleavable masses in vein and replacement deposits of intermediate temperature. Streak is grayish black. Enstatite Crystallography: Rhombic Colors : green, brown, colorless Hardness: 5.5 - 6 Specific gravity: 3.25 Refractive index: 1.658 - 1.668 Birefringence: .01 Occurrence: south Africa, Burma Comments:some chatoyant.Absorption line @ 506 nm $100 per ct. for faceted transparent stones Eosphorite ... childrenite .. hydrated manganese aluminum phosphate Crystal sys: monoclinic Color:pink to brown SG: 3.1 - 3.2 Hardness: 5 Comments: occurs in granite pegmatites with apatite, manganese phosphates and rose quartz Epidote...{ep'-i-doht} Crystallography: monoclinic Colors: dark brownish green,yellowish, red, yellow, gray Hardness:6.5 Specific gravity: 3.25 - 3.45 Cleavage: excellent Refractive index: avg. 1.75 v. .035 Birefringence: .019 - .045 Pleochroism: strong green, dark brown, yellow Comments: Color of crystals usually too dark to make good gemstones. strong dichroic. distinctive pistachio green. Epidote is the principal member of a group of silicate minerals that occur most commonly in low grade, calcareous metamorphic rocks and also in igneous rocks, where they have altered from feldspar, pyroxene, and amphibole minerals. A calcium aluminosilicate, epidote forms pistachio green to dark green elongated crystals, disseminated grains, or fibrous or granular masses that have perfect cleavage in one direction. Luster vitreous. Epsomite ... hydrous magnesium sulfate Crystal sys: orthorhombic Color: colorless to white SG: 1.67 Hardness: 2 - 2.5 Comments: epsom salts Erythrite ... hydrated cobalt arsenate Crystallography: monoclinic Colors: red to gray Luster: vitreous to pearly Hardness: 1.5 - 2.5 Specific gravity: 3.07 Cleavage: perfect Essonite ... see garnet ... hessonite Euclase Crystallography: monoclinic Colors: pale green or blue some yellow, colorless Luster: vitreous Hardness: 7.5 Specific gravity: 3.1 Cleavage : very good Refractive index: avg. 1.665 v. .019 Crystal or stone size: Comments: appearance & RI almost identical to fibrolite, distinguish by lower SG. Fauslite... see turquoise Comments: turquoise which zinc is the colorent Feldspar Types: orthoclase, microcline moonstone, labradorite, amazonite, albite, plagioclases, cat's eye, sunstone Ferberite ... heubnerite .. iron maganese tungstate Crystallography: monoclinic Colors: reddish brown, blackish brown, black Hardness: 5 - 5.5 Specific gravity: 7.1 - 7.5 Comments: main ore of tungsten Fergusonite (sp) ... see monazite Ferroaxinite ... manganaxinite .. hydrous calcium iron manganese borosilicate Color: reddish brown to yellow, violet and gray sometimes green when incrusted with clorite SG: 3.25 Hardness: 6.5 - 7 Comments: a rare and unusual gemstone Ferruginous quartz ... Monazite .. rare earth phosphate Crystallography: monoclinic Colors: yellow to brownish red Luster: vitreous to waxy Hardness: 5 - 5.5 Specific gravity: 4.8 - 5.5 Comments: ore of cerium and thorium Fibrolite Colors: pale blue, greenish Hardness:7.5 Specific gravity: 3.25 Cleavage : very good Refractive index: avg. 1.665 v. .019 Crystal or stone size: Comments: same RI as Euclase Flint...see quartz, chert, chalcedony, siliceous rock Color: white, gray, red, black, some zoned Comments Flosferri ... see aragonite Fluorite {flohr'-yt} fluor spar, blue John, Derbyshire spar Crystallography: isometric Colors : Purple, blue, green, yellow, pink, colorless Luster: vitreous Hardness: 4 Specific gravity: 3.18 Cleavage : perfect octahedral Refractive index: 1.434 Comments: Fluorite, calcium fluoride, is a major industrial mineral used as a flux in steel making as well as in the preparation of hydrofluoric acid and, in the ceramics industry, in glasses and enamels. Fluorite's vitreous, cubic crystals and cleavable, granular masses have a wide color range (often green, blue, or purple) and may fluoresce under ultraviolet light. Fluorite deposits form under a wide variety of conditions: as veins produced by hydrothermal alteration, as beds and cavities in sedimentary rocks, in hot spring deposits, and in pegmatites. Fossilized Wood ... Quartz group subtypes/ trade names: Agatized wood; Petrified wood, (brown, gray, red, white); some opal can be found in this; Comments: look under quartz Franklinite {frank'-lin-ite} see magnetite, loadstone Crystallography: isometric Colors: black Hardness: 5.5 - 6.5 Specific gravity: 5.2 Cleavage: none Comments: Franklinite is a zinc and iron manganese OXIDE MINERAL, that occurs abundantly only at Franklin, N.J., where, associated with zincite and willemite, it has been mined as an ore of zinc and manganese. A member of the SPINEL group, franklinite forms brilliantly metallic, iron black octahedral crystals, rounded grains, and granular masses in strongly altered limestone. Streak is reddish brown. GGG...cubic..Gadolinium gallium garnet colorless Hardness: 6.5 - 7 Specific gravity: 7.02 - 7.05 Cleavage: Refractive index: 2.03 Occurrence: man made Crystal or stone size: thumb size Gabbro...{gab'-roh}.. rock Comments Gadolinite...beryllium iron yttrium silicate Crystal sys: monoclinic Color: green, brown SG: 4 - 4.47 Hardness: 6.5 - 7 Comments: ore of yttrium, thorium and rare earth elements Galena {guh-leen'-uh}.. galenite .. lead sulfate Crystallography: cubic - hexoctahedral Colors:gray Luster: metallic Hardness: 2.5 - 2.75 Specific gravity: 7.4 - 7.6 Cleavage: perfect cubic Crystal or stone size: massive Comments Garnet see type: almandine, pyrope, hessonite(essonite), grossular, demantoid, topazolite, spessartine (sp), andradite, audradite(sp) Almandine (rhodolite) uvarovite (a rare intensely green stone) Colors : Green, to red, violet tint, brown tint Garnierite ... see serpentine Geode ... hollow rock .. sometimes lined with crystals .. see agate Geyserite ... see opal Glass Glauberite {glow'-bur-yt} sodium calcium sulfate Crystallography: monoclinic Colors: white, light yellow, gray to buff Luster: glassy Hardness: 2.5 - 3 Specific gravity: 2.7 - 2.8 Cleavage: perfect basal Occurrence: in and around salt beds Crystal or stone size: small 2 to 3 cm Comments: The EVAPORITE mineral glauberite, a sodium and calcium sulfate, occurs sparingly in the deposits left by evaporation of saline lakes. It forms brittle, tabular, and prismatic crystals with vitreous luster, pale yellow or gray color, good basal cleavage, and slightly salty taste. Glauberite also occurs as isolated crystals in clastic sedimentary rocks, volcanic cavities, and fumaroles. Glaucodot ... cobalt iron arsenic sulfide Crystal sys: orthorhombic Color: white or grayish white often with pink erythrite SG: 6.04 Hardness: 5 Comments: ore of cobalt Glauconite ... hydrous potassium aluminum iron magnesium silicate Crystal sys: monoclinic Color: light blue green SG: 2.5 - 2.8 Hardness: 2 - 2.25 Comments: because of potassium content it is used in textile, sugar and brewing. Glaucophane ... hydrous sodium magnesium aluminum silicate crystal sys: monoclinic Color: pale blue gray to dark blue and black SG: 3.08 - 3.3 Hardness: 6 - 6.5 Comments: of interest to petrologist as a means of defining the metamorphic conditions in which the surrounding rock formed. Gneiss...{nys}...rock .. less mica than schist otherwise much the same Crystal or stone size: massive Comments Goethite...{guh'-tyt}... hydrogen iron oxide Crystallography: orthorhombic Colors: black to brown to yellow Luster: adamantine to metallic to silky Hardness: 5 - 5.5 Specific gravity: 3.3 - 4.3 Cleavage: side pinacoid Comments: The widespread iron ore mineral goethite, an iron hydroxide is a common weathering product. It usually forms stalactitic masses with concentric or radiating internal structure. Color is yellowish to dark brown. Streak yellow. Cleavage perfect. Goethite is often associated with and indistinguishable from limonite in the gossan of sulfide mineral deposits, in tropical laterite, and in bog deposits Gold Crystal sys: isometric Color: yellow SG:15.3 - 19.3 Hardness: 2.5 - 3 Comments, Granite..{gran'-it}... coarse grained plutonic rock Color: light gray, white, pink or black and yellow brown Comments Granodiorite Comments: Granodiorite is a plutonic rock composed mainly of coarse plagioclase, QUARTZ, and a little potassium FELDSPAR. Hornblende (see AMPHIBOLE) and biotite (see MICA) may constitute about 20 percent of the rock, with small amounts of other accessory minerals. Granodiorite is intermediate between QUARTZ MONZONITE and quartz DIORITE. Batholiths in the Sierra Nevada containing large amounts of granodiorite often show intrusive relationships. They probably formed from the melting or transformation of sedimentary rocks in deep zones of mountain belts. Granophyre ... igneous rock Color: reddish to pink Comments: potassic feldspar, quartz. with: biotite, amphibole, sodic pyroxene, magnetite, ilmenite, muscovite, apatite, zircon, molybdenite, topaz, fluorite, etc. Graphite ... carbon Crystallography: hexagonal Colors: black Luster: submatallic Hardness: 1 - 2 Specific gravity: 2.3 Cleavage: perfect basal Crystal or stone size: rare tiny crystals in marble. Comments: greasy feel Graywacke...{gray'-wak} Comments: Graywackes are SANDSTONES composed of a mixture of abundant mineral and rock fragments, together with a fine grained clay matrix that constitutes from 15 to 50 percent of the rock. Graywackes vary widely in their mineral composition and may include fragments of biotite, chlorite, feldspar, hornblende, magnetite, pyroxene, quartz, and serpentine. Their color, as the name implies, is various shadings of gray. Graywacke beds, probably formed by DENSITY CURRENTS, are thin and graded, and they are generally found in geosynclinal areas of thick sediment accumulation. They date from nearly all geological ages, from the Precambrian Time to the Pleistocene Epoch. Greenockite ... cadmium sulfide Crystal sys: hexagonal Color: yellow SG: 4.9 Hardness: 3 - 3.5 Comments: ore of cadmium Grossularite ... grossular ...garnet Occurrence: metamorphosed limestone Gummite ... a mixture of several uranium oxides silicates, and salts Crystallography: none Colors: orange red to gray, yellow Luster: greasy to waxy Hardness: 2.5 - 5 Specific gravity: 3.9 - 6.4 Cleavage: none Comments: ore of uranium Gypsum {jip'-suhm} alabaster .. hydrous calcium sulfate Crystallography: monoclinic Colors: white and light tints may be dyed Luster: glassy to greasy to silky Hardness: 2 Specific gravity: 2.3 Cleavage: one direction perfect Occurrence: world wide Crystal or stone size: massive Comments: Gypsum, a hydrated calcium SULFATE MINERAL, is used as a raw material in plaster of Paris, as fertilizer, as an ornamental stone (alabaster and satin spar), and as optical material (selenite). Common gypsum is found as prismatic, curved, or twisting monoclinic crystals of vitreous luster and as earthy, foliated, or granular masses; alabaster as fine grained masses; selenite as colorless, transparent crystals or foliated masses; and satin spar as pearly, fibrous masses. Gypsum is soft clear, white, or tinted, and has perfect cleavage in one direction. It occurs with halite and other evaporite minerals in extensive beds, often alternating with limestone and shale, deposited in seas or playa lakes. Hackmanite .. see sodalite Color: light pink to light yellow Comments: this variety of sodalite, when exposed to SW UV causes yellow an colorless to change to bright orange for a very short time. Halite ... {hay'-lite}...salt Crystallography:isometric Colors: white, tinted blue, reddish Luster: glassy Hardness: 2.5 Specific gravity: 2.1 - 2.6 Cleavage: perfect cubic Crystal or stone size: Comments: Halite, sodium chloride (NaCl), is the most abundant of the EVAPORITE minerals. As rock salt, it is a major source of sodium and chlorine; as table salt, it is used to flavor food and is an essential dietary constituent Halite forms glassy, colorless, bluish or variously tinted cubic crystals and masses exhibiting perfect cubic cleavage Halite occurs with anhydrite, gypsum, and other evaporites, often in extensive beds left behind by evaporation of enclosed, salt water bodies (playas). When such deposits are buried and deformed, a plug or SALT DOME may be extruded through the overlying sediments. water soluble sometimes red fluorescent. Hambergite Colors: colorless Hardness: 7.5 Specific gravity: 2.35 Refractive index: avg. 1.587 v. .072 Comments: strong double refraction, collector stone @ $100 to $300 per ct. for outstanding faceted stones. Harmotome ... hydrated barium potassium aluminum silicate Crystal sys: monoclinic Color: white, gray, yellow, red or brown SG: 2.4 - 2.5 Hardness: 4.5 Comments: collector item Hauerite ... manganese sulfide Crystal sys: isometric Color: blackish brown SG: 3.5 Hardness: 3.5 - 4.5 Comments: scientific interest Hausmannite ... manganese oxide Crystal sys: tetragonal Color: blackish SG: 4.7 - 4.8 Hardness: 5 - 5.5 Comments: manganese ore Hauyne ... sodium calcium aluminum silicate sulfate Color: blue, white, green SG: 2.44 - 2.5 Hardness: 5.5 - 6 Comments: found in lapis, collector stone when it can be found large enough to cut. rare $ 2000 to $ 3000 per ct. blue Hedenbergite ... calcium iron silicate Crystal sys: monoclinic brown to light green SG: 3.58 - 3.6 Hardness: 5 -6 Comments: collector item Heliodore ... see beryl Heliolite .. see feldspar Color: brownish orange Hematite...{hee'-muh-tite}...haematite Crystallography: hexagonal Colors: metallic black, reddish Luster: high Hardness: 5.5-6.5 Specific gravity: avg. 5.1 Cleavage: none Refractive index: Occurrence: iron ore Crystal or stone size: Comments: The widespread iron oxide hematite is the most important ore mineral of IRON. Other uses include polishing compounds and paint pigments. Varying in color from reddish brown to black, it forms brilliantly metallic, tabular crystals as well as compact, fibrous kidney shaped or granular masses and CONCRETIONS. Streak is cherry red to brownish. Present in rocks of all types as an alteration product of earlier iron minerals, hematite is particularly abundant in the sedimentary rocks known as RED BEDS. It is usually slightly magnetic. Hemimorphite {hem-i-mohr'-fyt} calamine hydrated zinc silicate Crystallography: orthorhombic Colors: white stained Luster: glassy Hardness: 4.5 - 5 Specific gravity: 3.4 - 3.5 Cleavage: prismatic Crystal or stone size: 2 - 3 cm. Comments: The hydrated zinc silicate mineral hemimorphite, formerly called calamine, is an important ore of zinc. It forms rounded aggregates of white or tinted sheaf like crystals with perfect cleavage in one direction. Luster is vitreous. An alteration product of sphalerite, it occurs with other zinc minerals, particularly smithsonite, from which it is distinguished by its strong pyroelectricity. Fluoresces bright orange in LW UV. Herderite ... calcium beryllium phosphate Crystal sys: monoclinic Color: yellow, greenish white, purple SG: 2.9 - 3 Hardness: 5 - 5.5 Comments: collector item Heubnerite ... see ferberite Heulandite ... hydrated sodium calcium aluminum silicate Crystal sys: monoclinic Color: yellow, green, reddish orange SG: 2.2 Hardness: 3.5 - 4 Comments: collector item Hexagonite ... tremolite .. see actinolite Hiddenite...spodumene...kunzite Colors: light red to purple, colorless to yellow Hardness: 6.5 Specific gravity: 3.18 Cleavage: perfect in two directions Refractive index: avg.1.665 Birefringence: Pleochroism: strong in colorless, red to violet colors in the dichroscope and to the eye as the stone is turned. Hiddenite shows blue green and yellow green. The yellow type shows differences in depth of color as you turn the stone. Comments: biaxial +; Hornblende Crystallography: monoclinic Colors: green (adenine); blue green (parasite) to black Luster: glassy Hardness: 5 - 6 Specific gravity: 3 - 3.4 Cleavage: prismatic Occurrence: A mineral of metamorphic and igneous rocks, often replacing pyroxene (uralite ),also in solid crystalline aggregates. Crystal or stone size: often several in. long Comments: Fusible to a black glass. Hornfels...{hohrn'-felz} rock Comments: Hornfels is a fine grained, dense to granular METAMORPHIC ROCK formed mainly from sedimentary rocks and volcanic tuffs in the zones of contact metamorphism surrounding igneous intrusions. Hornfels can form at temperatures ranging from 200 deg to 800 deg C (1,392 deg to 1,472 deg F), depending on the depth and pressure, which respectively, cannot exceed 10 km (6 mi) and 3,000 bars. Recrystallization is as thorough as that of SCHIST but, because uniform pressures prevail during contact metamorphism, foliation does not occur. The texture is a mosaic of equal sized small grains. Mineralogic varieties are indicated by prefixing the term hornfels with the names of essential constituents, for example, biotite hornfels. Hyacinth ... see zircon Hyalite ... see opal Hypersthene...Magnesium iron silicate..bronzite Crystallography: orthorhombic Colors: brown to black Luster: bronze Hardness: 5 - 6 Specific gravity: 3.4 - 3.9 Cleavage: perfect in one direction Refractive index: 1.69 - 1.705 Crystal or stone size: good crystals are rare Comments: difficult to distinguish from augite. rock forming mineral. same as but with more iron than enstatite. Idocrase...{y'-duh-krays}...vesuvianite .. Californite Crystallography: aggregate of tetragonal xtals Colors : yellow, green, brown Luster: similar to jade Hardness: 6.5 (Californite: 5.5) Specific gravity: 3.38 (Californite: 3.3) Cleavage: none Refractive index: avg. 1.7 v. .015 Crystal or stone size: crystals very small aggregate massive Comments: Californite resembles jade. Idocrase, or vesuvianite, is a calcium aluminosilicate mineral commonly found in altered limestones. It forms prismatic crystals ( tetragonal system ) and columnar, granular, or massive aggregates that are usually brown or green. Luster is vitreous to resinous, Transparent crystals sometimes are cut as gemstones, and californite, a compact, green, jadelike variety found in California, is an ornamental stone. Ilmenite...{il'-muhn-yt}...iron titanium oxide Color: dark brown to black SG: 4.5 - 5 Hardness: 5 - 6 Comments: The iron and titanium oxide mineral ilmenite is present in small amounts in many igneous rocks and placer sands and is the principal titanium ore. Ilmenite forms iron black, thick tabular or acute rhombohedral crystals (hexagonal system), as well as thin plates, compact masses and embedded grains. Luster metallic to dull. Iron pyrite ...see pyrite Iolite...(see cordierite)...dichroite Ison glass...see mica Jadeite Crystallography: monoclinic Colors: green, white, brown, mauve, black orange red, yellow Luster: waxy Hardness: 6.5 - 7 Specific gravity: 3.33 v. .04 Cleavage: two directions perfect, but the aggregate structure does not easily cleave in ant direction. Refractive index: avg. 1.66 - 1.68 v. .012 Crystal or stone size: massive Comments Jasper Subtypes / trade names: Agate (name used by some, Quartz group), Egyptian; Riband; Basanite; Blood; Nunkirchner; Plasma; Silex; also see quartz Crystallography: none Colors: all Hardness: 7 Specific gravity: 2.55 Refractive index: avg.1.65 Crystal or stone size: massive Comments: Jasper is an opaque and fine grained quartz. Colored red, yellow, brown, or off white to gray by impurities, jasper has long been used as an ornamental stone because it takes a fine polish. The color of a streak made on a black jasper touchstone can determine with good accuracy the gold content of gold ores. Jet... coal Crystallography: amorphous Colors: black Luster: glassy dull Hardness: 2.5 Specific gravity: 1.33 Refractive index:avg. 1.66 Crystal or stone size: Comments: hot point test produces coal odor Kaolinite Crystallography: monoclinic Colors: white Hardness: 2 - 2.5 Specific gravity: 2.6 Cleavage: can be cut and shaped Occurrence: A mineral derived from aluminum silicates in the soil that has altered from feldspar in granite and pegmatite. Clay beds. Crystal or stone size: compact masses, dull and earthy white, stained red brown to black. Clay like Comments Kernite...see hematite Kimberlite...{kim-bur-lite} Kornerupine... also cat's eye Crystallography: orthorhombic Colors: green, brownish green, yellow Hardness: 6.5 Specific gravity: 3.32 Refractive index: avg. 1.675 Birefringence: .013 Occurrence: Sri Lanka, Burma, Kenya Crystal or stone size: Comments: strongly dichroic;confused w/tourmaline biaxial - Kunzite ...(see spodumene) Kyanite Crystallography: triclinic Colors: blue, some green, colorless Hardness: 4 in one direction to 7 in the other Specific gravity: 3.69 Cleavage: easy in one direction Refractive index: avg. 1.72 v. .019 Pleochroism: strong; colorless, dark blue violet and blue. Occurrence: can be found in NC Crystal or stone size: Comments: biaxial - The aluminum SILICATE MINERAL kyanite (derived from the Greek kyanos, meaning "blue") is used in the manufacture of spark plugs, porcelain, and other refractories; it has the same chemical composition as ANDALUSITE and SILLIMANITE. Its long bladed, usually blue crystals are distinctive. Luster is vitreous to pearly. Cleavage is perfect in one direction. Kyanite occurs in GNEISSES, SCHISTS, and granite PEGMATITES; it is an indicator of deep-seated, regional metamorphism of clay rich sediments. Labradorite...(see feldspar) Crystallography: triclinic Colors: white, yellow, reddish, gray to black Luster: glassy Hardness: 6 - 6.5 Specific gravity: 2.6 - 2.8 Cleavage: good in two directions Occurrence: labradorite (sp) found in Labrador Crystal or stone size: not common except albite (cleavelandite), moonstone Comments: bluish to whitish internal flashes in moonstone and labradotite Lamprophyre...{lam'-proh-fire} Comments: Lamprophyre is a dark-colored igneous rock composed of large crystals (phenocrysts) of iron and magnesium-rich minerals, such as hornblende (see AMPHIBOLE), biotite (see MICA), or PYROXENE, set in a fine grained, dark-colored groundmass. Lamprophyres commonly occur as dikes or sills. Most of them contain less than 46% silica by weight and are high in sodium and potassium. Lamprophyric magma is commonly rich in volatile compounds such as water and carbon dioxide. Latite...{lay'-tite} Comments: Latite is a medium colored igneous rock composed of large crystals of plagioclase and potassium feldspar set in a fine grained groundmass. Latites commonly occur as dikes or sills. Chemically, latite is a fine grained equivalent of monzonite. Lapis lazuli...{lap'-is laz'-u-lee} lazurite, lazulite, scorzalite Crystallography: monoclinic Colors: blue Luster: waxy Hardness: 5.5 Specific gravity: 2.8 Cleavage: poor Refractive index: 1.5 Crystal or stone size: massive Lazulite...hydrous magnesium aluminum phosphate Crystal sys: monoclinic Color: blue SG: 3 - 3.1 Hardness: 5 - 6 Comments: ornamental stone Lazurite ... sodium calcium aluminum silicate sulfate Crystal sys: tetragonal Color: blue, white, gray, pink SG: 2.55 - 2.74 Hardness: 5 - 6.6 Comments: collector item Leadhillite...sulfate & carbonate of lead... Pb4(SO4)(CO3)2(HO)2 Crystal: monoclinic (looks like hexagonal) Color: white tinged with yellow, blue, or green Luster: pearly to adamantine Cleavage: prominent, almost micaceous Hardness: 2.5 SG: 6.3 - 6.4 Fracture: conchoidal Translucent to transparent Comments: fluoresces orange Legrandite ...see adamite Lepidocrocite...see hematite Lepidolite...basic fluosilicate of lithium, potassium, and aluminum Leucite...potassium aluminum silicate Colors: colorless Hardness: 6 Refractive index: 1.504 - 1.509 Crystal or stone size: Comments: some color caused by thin repeated twinning laminate Lepidocrocite ... hydrous iron oxide Color: red, brown SG: 4 Hardness: 5 - 5.5 Comments: iron ore Lepidolite...hydrous potassium lithium aluminum Ver: zinnwaldite, silver gray to brown silicate Color: pink to lilac SG: 2.8 - 2.9 Hardness: 2.5 - 4 Comments: ore of lithium Leucite...potassium aluminum silicate Color: white SG: 2.5 Hardness: 5.5 - 6 Comments: fertilizer Libethenite...copper phosphate... Cu2(OH)PO4 Crystal system: rhombic bipyramidal Color: dark olive green Luster: resinous Hardness: 4 SG: 3.6 - 3.8 Fracture: subconchoidal Cleavage: 2 good Comments: Like olivenite, brochantite, and malachite, (likely associations), is one of the secondary minerals formed in the alteration through weathering of sulfide ore minerals. Lignite ... coal Color: black Limonite...{ly'-muh-nite}...stalactites...goethite Crystallography: orthorhombic or amorphous Colors: brown black to ocher yellow Luster: glassy to dull Hardness: 5.5 Specific gravity: 2.7 - 4.4 Cleavage: none Crystal or stone size: Comments Limestone...rock... calcium carbonate (calcite) in a very fine granular structure Color: gray Hardness: 3 SG: approx 2.7 Cleavage: brittle Comments: Limestone is easy to scratch acid will dissolve. some limestone was chemically precipitated, other in beds of accumulated lime removed from seawater by living organisms. Beds of clean limestone can only form father out in the sea and in deeper water beyond the distance that stream borne clay particles and sand can travel. Often remains of the organic life of the sea of the period of the lime deposition are included in the beds. These are fossils. Linarite...hydrous lead copper sulfate Color:blue Crystal sys: monoclinic SG: 5.35 H: 2.5 Comments: crystals to 4 in. Lindgrenite...see powellite Lintonite...(sp) local name in Michigan Color: green to grayish green Hardness: 5 - 5.5 Comments: sometimes confused with jade Liroconite...hydrated copper aluminum arsenate... Cu2Al(AsO4)(OH)4.4H2O Crystal system: monoclinic - prismatic Color: sky blue to greenish blue Luster: glassy Hardness: 2 - 2.5 SG: 3 Streak: pale blue Cleavage: 2, poor, brittle. Comments: translucent. Blowpipe turns it deep blue, then blackens, fusing to a black bead. Soluble in acid. Lithiophilite...isomorphous series of lithium, iron, and manganese phosphate LiMnPO4 (Triphylite LiFePO4) Crystal system: orthorhombic Color: gray blue to gray blue green (triphylite), pink to greenish brown (lithiophilite) Luster: glassy Hardness: 4.5 - 5 SG: 3.4 - 3.6 Cleavage: 1 fair, 2 imperfect Fracture: uneven to small conchoidal Comments: Brittle, transparent to translucent. Fuse on charcoal to black bead. Triphylite bead magnetic. Lithophysae...see cristobalite & tridymite (polymorphs of quartz) Loadstone ... see magnetite Color:black to dark brown Loellingite...FeAs2... diarsenide of iron Crystal system: orthorhombic - bioyramidal Color: tin white Luster: metallic Hardness: 5 - 5.5 SG: 6.2 - 8.6 Cleavage: basal Varieties: nickelin, cobaltian loellingite Comments: sometimes found with cobalt and nickel. Arsenic approx. 68 %; when heated gives garlic odor Luzonite... see enargite Magma... melted rock well below the surface of the earth; called lava when it reaches the surface. Magnesite ... magnesium carbonate Crystal sys: hexagonal Color: white, yellow, gray SG: 3 Hardness: 3.5 - 4.5 Comments: The carbonate mineral magnesite is a source of magnesia, used in the manufacture of refractory brick and various chemicals and pharmaceuticals. Color is white (gray-to-brown with impurities), Luster is vitreous. A compact, earthy form occurs when carbonic acid alters rocks containing serpentine or peridotite; a cleavable (rhombohedral) aggregate form occurs when metamorphism alters magnesium rich rocks, or when magnesium solutions replace limestone rocks. Major deposits are in Manchuria, Austria, Washington, and Nevada. Magnetite ... iron oxide Color: black SG: 5.2 Hardness: 5.5 - 6.5 Comments: ore of iron, strongly magnetic Malachite...copper carbonate Malacolite ... see diopside & hedenbergite Manganapatite...see apatite Manganite...manganese oxide... MnO(OH) Crystal system: monoclinic - prismatic Color: steel gray to black Luster: submatilic Hardness: 4 SG: 4.2 - 4.4 Streak: reddish brown Cleavage: perfect side, poor prismatic and basal Comments: Formed at higher temps than other manganese oxides, in veins. Manganocolumbites...see columbite & tantalite Manganotantalites...see columbite & tantalite Marble...forms in regional metamorphism from another single mineral sedimentary rock, like sandstone is a rock in which no major change can take place other than a growth and cementation of the individual crystal units. Marble forms from limestone and dolomite. Color: multi colored depending on containts Hardness: 3 - 4.5 Marcasite Crystallography: orthorhombic Colors: silver black Luster: metallic Hardness:6 Specific gravity: 4.9 Margarite ... hydrous calcium aluminum silicate Color: pink, white or grat aggregates SG: 2.99 - 3.1 Hardness: 3.5 - 4.5 Comments: can be found in NC, PENN, collector item Marialite...sodium & calcium aluminum silicate, with chlorine, carbonate, and sulfate; sodium and calcium mutally replace each other to any amount, making a series which have been named marialite for the NaCl rich end member and meionite for the CaCO end Crystal system: tetragonal Color: colorless - white, violet, pink, gray Luster: glassy Hardness: 5.5 - 6 SG: 2.5 - 2.7 Comments: fluorescent orange to bright yellow, less often red. Marl Comments: A sedimentary rock, marl is a white, gray, or brownish earthy mixture of fin grained calcium carbonate and clay. Formed in both marine and freshwater environments marl commonly contains fossil shells. It is used as a fertilizer and in the manufacture of insulation, portland cement, and bricks. Some marl, such as the potassium rich glauconite, or green sand, marl of the Atlantic coasts of Europe and the United States, is used in water softeners. Marmolite...see serpentine Marshite...see calomel Martite...see magnetite Massicot... PbO...Litharge...PbO lead oxide Crystal system: rhombic Color: yellow to red Luster: greasy to dull Hardness: 2 SG: 9.7 Cleavage: several Comments: association with galena Melanite ... see andradite Melanterite...see chalcanthite Meneghinite...see jamesonite Mercury ... Hg Color: silver SG: 13.6 Hardness: soft heavy liquid Comments (there are a lot of them...) Mesolite ... see natrolite Meteorite ... see iron and pyrrhotite Miargyrite...antimony sulfide ...AgSbS2 Crystal system: monoclinic Color: black to gray Luster: metallic Hardness: 2 - 2.5 SG: 5.1 - 5.3 Streak: cherry red Cleavage: 3 poor Fracture: subconchoidal Comments: rare, never forming large crystals. Silver ore. Mica group...{my'-kuh}...muscovite...biotite...phlogopite Crystallography: monoclinic prismatic Colors: colorless, light yellow, amber, rose, green, gray, black Luster: glassy Hardness: 2 - 2.5 Specific gravity: 2.8 - 3 Cleavage: perfect basal Crystal or stone size: common flat transparent used as windows in stoves; plates are flexible. Comments Micaceous hematite Comments: see hematite; hematite with mica. Mica schist...conglomerate rock containing a large amount of mica (see mica) Microcline...(see feldspar)...green feldspar...amazonstone Crystallography: triclinic Colors: light cream, yellow, brown, green to black. Luster: resinous Hardness: 6 Specific gravity: 2.5 - 2.6 Cleavage: two directions good Occurrence: pegmatite dikes Crystal or stone size: inches to feet Comments: gemstones and scouring powder Microlite...hydrous sodium calcium tantalum oxide Crystal sys: isometric Color: brown, colorless, yellow SG:4.2 - 6.4 Hardness: 5 - 5.5 Comments: VA,MA,CN, collector item Migmatite...anatexite...ultrametamorphic rock Colors: dark to light gray Occurrence: Precambrian shields Uses: building stone, sometimes as polished slabs for ornamental purposes. Millerite ... nickel sulfide Crystal sys: hexagonal Color: brassy yellow SG: 5.2 - 5.6 Hardness: 3 - 3.5 Comments: The nickel sulfide mineral millerite (NiS) is a minor ore of nickel. It forms slender to capillary, brass to bronze yellow crystals, often in radiating needles, interwoven hairs, or tufted coatings. Luster metallic, streak greenish black. A low temperature mineral, millerite occurs as a lining in cavities, geodes, and carbonate veins; as an alteration, or weathering, product of other nickel minerals; and as inclusions in other minerals. Mimetite...{mim'-uh-tyt}...mimetesite...lead arsenate chloride Crystallography: monoclinic Colors: colorless, yellow brown to orange Luster: resinous to adamantine Hardness: 3.5 Specific gravity: 7.1 Cleavage: none Crystal or stone size: small long crystals Comments: The lead arsenate mineral mimetite is a minor ore of lead, occurring in the oxidation zone of lead veins. Its name is derived from its ability to "mimic" pyromorphite, a similar but more common mineral in which the arsenic is replaced by phosphorus. Mimetite forms crusts and prismatic or barrel shaped crystals (hexagonal system) that are pale or orange yellow to brown. Luster, resinous; and its an ore of lead. Minium...see massicot Mispickel...arsenopyrite Crystallography: monoclinic Colors: sliver white Luster: metallic Hardness: 5.5 - 6 Specific gravity: 5.9 - 6.2 Cleavage: prismatic Crystal or stone size: Comments: garlic smell with hammer blow, ore of arsenic Moldavite...tektites from Czechoslovakia Colors: gray, black, green Luster: glassy Hardness: 5 Specific gravity: 2.35 Refractive index: 1.49 Crystal or stone size: Comments: volcanic glass Molybdenite...{muh-lib'-duh-nyt}... molybdate Crystallography: hexagonal Colors: bluish gray Luster: greasy Hardness: 1 - 1.5 Specific gravity: 4.7 Cleavage: perfect along plates Occurrence: tabular crystals with hex outline interwoven masses common Comments: The chief ore of molybdenum is the molybdenum sulfide mineral molybdenite. Usually found in foliated or granular masses and scales, molybdenite occasionally forms lead gray, six sided tabular or prismatic crystals. Its luster is metallic. Because of its softness and perfect basal cleavage, it has a greasy feel and is useful in making special lubricants. Its streak (greenish or bluish gray). SG (4.7) distinguish it from graphite (dark black and 2.23), which has similar physical properties. Widespread but rarely abundant, molybdenite occurs in acid igneous rocks, such as granite in contact metamorphic deposits; in pegmatite; and in high temperature quartz veins. The world's most important deposit is at Climax, Colorado. Monazite...{mahn'-uh-zyt} Comments: The chief ore of thorium and the rare earths is the phosphate mineral monazite. It commonly forms small flattened or elongated crystals (monoclinic system) that are a resinous, reddish to yellowish brown. Hardness is 5 -5.5, streak is white, and specific gravity is 4.6-5.4. Monazite occurs as an accessory mineral in granites, gneisses, and pegmatites and as rounded grains in the sands formed from their weathering. The thorium-rich varieties are radioactive and have been used in geologic dating. Monzonite...{mahn'-zuh-nyt} rock Comments: The coarse-grained plutonic rock monzonite, which results from deep igneous or metamorphic processes, contains approximately equal amounts of potassium and plagioclase feldspars and little or no quartz. Dark minerals, such as pyroxene and hornblende, make up 30 to 40 percent of the rock. Monzonite is intermediate between syenite and diorite. Moonstone...see albite, orthoclase (plagioclase feldspar) Morganite...see beryl...mortor Colors: rose pink to red, light pink to colorless Hardness: 7.5 Specific gravity: 2.8 Refractive index: avg. 1.59 v. .008 Mossottite...see aragonite Mottramite...(Zn,Cu)Pb(VO4)(OH)... lead zinc - copper ...Descloizite...(Cu,Zn)Pb(VO4)(OH) Crystal system: rhombic Color: yellow brown to cherry red, brown, green, or black Luster: greasy Hardness: 3.5 SG: 5.9 mottramite... 6.2 descloizite Streak: yellow orange to brown red Fracture: small conchoidal Cleavage: none Comments: associated with wulfenite and vanadinite Muscovite...var. fuchsite, alurgite, mica ...hydrous potassium aluminum Crystallography: monoclinic Colors: silver white, yellow, gray, brown Luster: glassy Hardness: 2 - 2.5 Specific gravity: 2.76 - 2.88 Cleavage: perfect along plates Crystal or stone size: tabular crystals w/pseudo -hex outline, up to 30 - 50 sq. yds. Comments: usually scaly laminae masses Mylonite...{my'-luh-nyt} Comments: Ductile, as opposed to brittle, processes dominate the formation of the metamorphic rock mylonite in deep seated fault zones. Mylonite is commonly foliated and may contain fine grained quartz, feldspar, and micas surrounding much larger feldspar or sometimes quartz grains or other minerals that have been greatly flattened and drawn out in the foliation. Mylonite zones, which may vary in width from a few millimeters to several kilometers, occur in the central portions of recent mountain chains and in the roots of old mountain chains. Nantokite...see calomel Naphtheline...(sp) Nepheline, igneous rock .. nephelin w/ olivine augite, titnite, perovskite, melilite noselite, sodalite, or hauyne. Crystallography: none Colors: light gray, pin, green Hardness: ver. Specific gravity: ver. Crystal or stone size: massive Comments: Nepheline, the most common of the group, is a white to gray mineral that is distinguished from the feldspars, which it resembles, by its poorer cleavage and slightly greasy luster. It occurs as grains or large masses in many alkaline igneous rocks ranging from magnesium rich nepheline basalts to granitelike but quartz free nepheline syenites. It is also found in some metamorphic rocks, particularly the nepheline gneisses of Ontario, Canada. Natrolite...hydrated sodium aluminum silicate Crystallography: orthorhombic Colors: white Luster: vitreous to pearly Hardness: 5 - 5.5 Specific gravity: 2.2 - 2.26 Crystal or stone size: 3 ft. x 6 in. in Canada Comments: found with asbestos, collector mineral Nephrite ... tremolite ... actinolite...(jade) Crystallography: monoclinic Colors: green, white, black Hardness: 6.5 Specific gravity: 2.96 Refractive index: 1.62 Comments: usually classed with jadeite as jade. Neptunite ... sodium potassium iron titanium silicate Color: dark brown to black SG: 3.23 Hardness: 5-6 Comments: collector item Niccolite ... nickeline .. nickel arsenide Crystallography: hexagonal Colors: pink bronze, pale green film Luster: metallic Hardness: 5 - 5.5 Specific gravity: 7.78 Cleavage: none Crystal or stone size: rare small crystals Comments: ore of nickel Nicholsonite...see aragonite Nickeline ... see niccolite Niter... potassium nitrate (saltpeter) ...KNO3 Color: white Luster: glassy Hardness: 2 SG: 2.1 Comments: found in caves, short fibers on rock surface and floors. Norbergite Obsidian...volcanic glass Crystallography: none Colors: black Luster: glassy Hardness: 5 Specific gravity: 2.35 Cleavage: none Refractive index: 1.49 Occurrence: lava flows Crystal or stone size: can be massive Comments Octahedrite ... see anatase Odontolite ... very similar to turquoise Colors: blue green Hardness: 5 Specific gravity: 3.1 Refractive index: 1.6 Crystal or stone size: Comments: can be confused with turquoise Oligoclase...(see feldspar) Olivine...olivenite... magnesium iron silicate ...forsterite...fayalite ...gem variety peridot Omphacite...calcium magnesium iron aluminum silicate Crystal sys: monoclinic Color: light green SG: 3.29 - 3.37 Hardness: 5-6 Comments: collector crystal usual found in quartz Onyx Colors: white, usually dyed to any color Hardness: 7 Specific gravity: 2.6 Refractive index: 1.535 + - .004 Crystal or stone size: massive Comments: used for carvings, building stone Opal ... black, fire, white, water Ophiolite... see serpentine Orpiment... arsenic sulfide Color: golden yellow to orange SG: 3.48 Hardness: 1.5 - 2 Comments: ore of arsenic, used in hide tanning Orthite....(Allanite) Orthoclase...orthose...(see feldspar)...moonstone ...plagioclase...albite...adularia Colors: colorless with floating blue sheen, light yellow, white, see below Hardness: 6 - 6.5 Specific gravity: 2.56 Cleavage: perfect in two directions Refractive index: 1.52 - 1.526 Crystal or stone size: Comments: 4 ray star in green, brown, orange, brown and black. It may be completely transparent, and the sheen can be either silvery white or a soft but distinct blue. The blue or white sheen is called adularscent, and is caused by the presence of tiny crystals of albite arranged in layers within the host microline. The adularscent sheen resembles a cloud of light that appears within the gem when it is turned at the right angle to the eye. Moonstones come mainly from India, Sri Lanka, Burma, Canada, Brazil, and others. Painite Colors: dark red Hardness: 8 Specific gravity: 4.01 Refractive index: 1.8 +- .029 Pleochroism: pale brown orange to ruby red Comments: uniaxial (-) Pargasite... see hornblend Pearl...white, pink, bronze, black, gray, blue... freshwater ... conch is pink, clam is black. Biwa (fresh water), Mabe (dome), baroque (odd shape) Colors: white to cream, Australian is silver white, venezuelan is translucent Pectolite Pegmatite...{peg'-muh-tyt} ...igneous rock Penninite ... see chlorite ... pennine Pentlandite ...{pent'-luhnd-yt} see pyrrhotite Comments: The nickel and iron isometric sulfide mineral pentlandite is the principal ore of nickel. Forming light bronze yellow, granular aggregates in basic igneous rock, it is nearly always intimately associated with and hard to distinguish from pyrrhotite. Hardness is 3.5, luster is metallic, streak is light brown, and specific gravity is 4.6-5.0. At nickel mines in Sudbury, Ontario, and elsewhere, the pentlandite pyrrhotite aggregate is crushed, and the pyrrhotite is magnetically separated from the nonmagnetic pentlandite. Periclase... see brucite Peridot ...(see olivine) Occurrence: green type from Red Sea, Arizona Burma, etc. Peridotite...pyroxenite Colors: green, blue, black Occurrence: world wide Comments: a rock, a dunite Perlite...A glass froth which swells with heat or water found in old obsidian flows. A man product is sold as perlite. Petalite ... lithium aluminum silicate Crystallography: monoclinic Colors: colorless, white Luster: vitreous to pearly Hardness: 6 - 6.5 Specific gravity: 2.41 Cleavage: perfect Crystal or stone size: Comments: ore of liyhium Phacolite ... see chabazite Phenacite...phenakite Crystallography: hexagonal Colors: colorless to white Luster: glassy Hardness: 7.5 to 8 Specific gravity: 2.96 to 3 Fracture: conchoidal Cleavage: poor Refractive index: avg. 1.662 v. .016 Occurrence: a mineral of pegmatites and high temperature veins. Comments: bright silvery appearance. Phlogopite... potassium, magnesium, aluminum silicate ...K(Mg,Fe)3(AlSi3)O10(F,OH)2 Crystal system: monoclinic - prismatic Color: light to dark brown Luster: pearly to metallic Hardness: 2.5 - 3 SG: 2.7 Cleavage: perfect basal, yielding thin, flexible and elastic plates Comments: translucent, 6 or twelve ray star not uncommon. Unlike muscovite makes a cloudy solution if boiled in strong sulfuric acid. Phonolite ... igneous rock Crystallography: none Colors: light gray, green, brown, pink Luster: greasy Hardness: Varies Occurrence: in US, COL, SD, MONT. Crystal or stone size: massive Comments: building stone Phosgenite...chlorocarbonate of lead... Pb2(CO3)Cl2 Crystal system: tetragonal trapezohedral (4 2 2) Color: colorless, white, yellowish brown to gray Luster: adamantine Hardness: 2.5 - 2.75 SG: 6 - 6.1 Fracture: conchoidal Cleavage: good prismatic, poor basal Comments: slightly sectile, transparent to translucent, fluoresces a brilliant orange yellow Phosphophyllite ... hydrated zinc iron manganese phosphate Crystallography: monoclinic Colors: blue green Luster: vitreous Hardness: 3 - 3.5 Specific gravity: 3 - 3.1 Crystal or stone size: long prismatic or thick tabular crystals are rare up to 4 in.; massive Comments: sometimes faceted into gems for collectors Phosphuranylite Phyllite Picrolite...see serpentine Pinite...see spodumene Pisanite...see chalcanthite Pisolitic ... see bauxite Pitchblende ... see uraninite Platinum Color: silver gray SG: 14 - 19 Hardness: 4 - 4.5 Comments Plagioclase...see feldspar Polybasite ... silver copper antimony sulfide Crystallography: monoclinic Colors: iron black Luster: metallic Hardness: 2 - 3 Specific gravity: 6 - 6.2 Crystal or stone size: small, collector Comments: ore of silver Polycrase... see monazite Polyhalite Porphyry ... igneous rock .. diorite Crystallography: none Colors: gray, green, reddish to bluish Hardness: varies Specific gravity: varies Comments: facing on buildings, marble like. Powellite Prehnite...{pray'-nyt} Crystallography: orthorhombic Colors: pale greenish yellow, yellow, white Luster: glassy Hardness: 6 Specific gravity: 2.87 Cleavage: basal Refractive index: avg. 1.63 v. .03 Occurrence: N.J., CN, Mass., Quebec Crystal or stone size: crystals usually small, stone massive. Comments: The calcium-aluminum silicate mineral prehnite, which may be pale to dark green, gray, white, yellow, or colorless, is sometimes cut and sold as Cape emerald. Often associated with zeolite minerals, it usually lines the cavities of basaltic rocks. Prehnite frequently forms lamellar or rounded masses; tabular or prismatic crystals (orthorhombic system) are found more rarely. Ornamental stone that sometimes is confused with jade. Proustite...{proost'-yt}...silver arsenic sulfide Crystallography: hexagonal Colors: dark red Luster: adamantine Hardness: 2 - 2.5 Specific gravity: 5.57 Cleavage: good rhombohedral Refractive index: Crystal or stone size: up to 6 in. Comments: The silver arsenic sulfide mineral proustite, or light ruby silver, is a minor ore of silver. Scarlet to vermilion in color and streak, proustite forms compact masses and prismatic, rhombohedral, or scalenohedral crystals (hexagonal system) often associated with PYRARGYRITE, or dark ruby silver, in silver veins. luster is adamantine to submetallic. Prized mineral for collectors. Psilomelane...{sy-loh-mel'-ayn}...romanechite .. hydrous barium manganese oxide Crystallography: orthorhombic Colors: brown, black Luster: submetallic Hardness: 5 - 7 Specific gravity: 3.7 - 4.7 Crystal or stone size: masses never in crystals Comments: Psilomelane, a basic oxide mineral of barium and manganese, is, after pyrolusite, the most important manganese ore. It forms iron-black to steel-gray concretionary or earthy masses that have a submetallic or dull luster, streak brownish black. Formed by the weathering and alteration of manganese carbonates, psilomelane frequently is associated with pyrolusite and other secondary manganese oxides and with clay and hydrated iron oxides. Greasy feel. Pumice...{puhm'-is}... igneous rock Crystallography: none Colors: gray, yellowish, red Specific gravity: v. sometimes less than water Occurrence: material expelled by volcanos Crystal or stone size: massive Comments: Pumice is a frothy volcanic glass, usually light in color and high in silica. It occasionally contains some crystals of quartz and feldspar. The froth, which forms during an eruption of a gas rich magma because of the decrease in confining pressure, is similar to the bubbles formed in carbonated beverages when their containers are opened. The bubbles make pumice so light that it will float on water. Pumice, which may float for weeks before it becomes waterlogged and sinks, has been found floating as many as 6,400 km (4,000 mi) from its source. Pumice is used primarily for abrasives, polishing compounds, insulators, and lightweight aggregates and in stucco, plaster, and cement. very porous, may float Purpurite ... manganese iron phosphate Crystal sys: orthorhombic Color: purple to red with brown to black surface alteration SG: 3.4 Hardness: 4 - 4.5 Comments: SD,CA collector item Pycnite... see topaz Pyralspite ... see garnet Pyrargyrite... silver antimony sulfide Crystallography: hexagonal Colors: black w/dark red tints Luster: submetallic Hardness: 2.5 Specific gravity: 5.85 Crystal or stone size: masses or disseminated grains Comments: purple red streak, minor silver ore Pyrite...{py'-ryt} Crystallography: cubic Colors: brassy yellow Luster: metallic Hardness: 6 Specific gravity: 4.9 - 5.02 Cleavage: none Comments Pyrochlore ... see microlite Pyrolusite ...manganese oxide... polianite Crystallography: tetragonal Colors: black Luster: greasy Hardness: 6 - 6.5 Specific gravity: 4.7 - 5 Crystal or stone size: aggregates and masses Comments: earthy ver. very soft and greasy ore of manganese Pyromorphite ... lead phosphate chloride Crystallography: hexagonal Colors: green brown, colorless Luster: resinous to adamantine Hardness: 3.5 - 4 Specific gravity: 6.7 Cleavage: none Occurrence: PENN., IN US Crystal or stone size: aggregates and masses Comments: minor ore of lead Pyrope ...see garnet ...magnesium aluminum silicate Crystallography: isometric Colors: red, best is blood red Luster: vitreous Hardness: 7.5 Specific gravity: 3.7 - 3.9 Cleavage: none but splinters Refractive index: 1.73 - 1.76 Crystal or stone size: gem, up to 20 cts Pyrophanite...see Ilmenite Pyrophyllite...{py-roh-fy'-lyt} hydrous aluminum silicate... var. agalmatolite, pagodite Crystallography: monoclinic Colors: yellow, white, pale green, brown Luster: pearly to greasy Hardness: 1 - 2 Specific gravity: 2.8 Occurrence: NC, SC, AR, GA. IN US Crystal or stone size: massive, used for carving Comments: flexible but not elastic. Pyrophyllite a hydrous aluminum silicate mineral, often resembles talc in its appearance, properties, and uses. It forms foliated, radiating, or fibrous aggregates and compact to granular masses that have a greasy feel and are pale colored. Mohs hardness is 1 to 2, luster is pearly to dull and glistening, and specific gravity is 2.65 to 2.90. Pyrophyllite is the main component of some schists and also occurs in hydrothermal veins with quartz and micas. Pyroxenite ... igneous rock .. var. websterite, bronzitite Contains: pyroxene with some or all of olivine, hornblende, chromite magnetite, ilmenite sulfide biotite, garnet, apatite. Crystallography: none Colors: dark green, brown, black Crystal or stone size: massive, coarse grain Comments: building stone Pyroxmangite ... see rhodonite Pyrrhotite ... ferrous sulfide Crystallography: pseudohexagonal Colors: bronze Luster: metallic Hardness: 4 Specific gravity: 4.6 - 4.7 Cleavage: none Crystal or stone size: massive Comments: magnetic Quartz Subtypes Quartzite ... metamorphism of sandstone Colors: brown, yellow, gray, reddish, white Hardness: ver. see quartz Specific gravity: ver. Cleavage: none Occurrence: world wide Crystal or stone size: massive Comments: very small grains of quartz firmly together Radelerz ... see bournonite Rammelsbergite... see loellingite Realgar ... arsenic sulfide Crystallography: monoclinic Colors: orange red Luster: resinous Hardness: 1.5 - 2 Specific gravity: 3.4 - 3.5 Cleavage: perfect Crystal or stone size: crystals common Comments: could be mistaken for cinnabar ore of arsenic, very unstable Rhodochrosite...{roh-duh-kroh'-syt}...manganese carbonate Crystallography: hexagonal Colors: pink, gray, brown Luster: vitreous to pearly Hardness: 3.5 - 4 Specific gravity: 3.4 - 3.6 Cleavage: perfect rhombohedral Refractive index: 1.597 - 1.817 Crystal or stone size: massive Comments: ornamental stone, crystals rare. The manganese carbonate mineral rhodochrosite is a minor ore of manganese used mainly as a decorative stone and gemstone. Typically displaying shiny rose-red, intricately banded surfaces, it forms granular to compact cleavable masses, crusts, or columns. Streak is white. It occurs in moderate to low-temperature hydrothermal ore veins, particularly of silver, lead, zinc, and copper, as well as in high temperature metamorphic deposits. Rhodonite...{roh'-duh-nyt}...manganese silicate Crystallography: triclinic Colors: violet red to flesh red Hardness: 5.5 - 7 Specific gravity: 3.3 - 3.68 Cleavage: two directions perfect Refractive index: 1.72 - 1.744 Crystal or stone size: massive Comments: ornamental stone usually with black inclusions. The manganese, iron, and calcium silicate mineral rhodonite is valued not only as a rose-red ornamental stone but also as a major ore of manganese in India. Usually associated with rhodochrosite and other manganese minerals, it forms large, rounded, tabular crystals (triclinic system) or cleavable, compact masses. luster is vitreous, streak is white. Rhodolite ...see garnet Colors: violet red to brownish red violet Specific gravity: 3.84 Refractive index: 1.76 Comments: a cross between almandite & pyrope Rhyolite ... a volcanic rock Colors: shades of gray, yellow, pale to deep red Luster: glassy Hardness: 6 - 6.5 Specific gravity: v. Occurrence: volcanic Crystal or stone size: massive Comments: it may contain many minerals, biotite quartz, hornblende, opal, feldspar, magnetite. Rhyolite is a light-colored, fine grained volcanic rock with a very high (more than 70%) silica content. It often contains phenocrysts of quartz and feldspar in a glassy matrix. Iron and magnesium minerals are rare or absent. Similar to the coarser grained granites in mineralogy and chemistry, rhyolite tends to be very viscous because of its high silica content, and upon eruption it generally forms steep-sided domes and plugs. Gas rich rhyolite, however, erupts violently to form welded tuffs, or ignimbrites, and may spread out over great distances. Richterite ... hydrous sodium magnesium silicate Color: purple red to yellow SG: 2.97 - 3.46 Hardness: 5-6 Comments: in crystal form a collector item Rockbridgeite... see dufrenite Rosolite Crystallography: monoclinic Colors: deep rose to pink Luster: glassy Hardness: 3.5 Specific gravity: 3.5 - 3.7 Cleavage: easy Refractive index: unable to find info Occurrence: now found in cobalt mines in Morocco. Crystal or stone size: small, rare Comments: collector gem, too soft and rare for jewelry. Rubellite ... see red tourmaline Ruby ... red corundum Rutilated quartz ...see rutile and quartz Rutile...{roo'-teel}...titanium oxide Comments: synth. is common. A minor ore mineral of titanium, is the most stable of three naturally occurring forms of titanium oxide see OXIDE MINERALS). Rutile forms prismatic or needlelike crystals (tetragonal system), most commonly red-brown in color, streak is pale brown, luster is adamantine to metallic, Widespread in small amounts, rutile occurs in intermediate basic igneous rocks as a high-temperature accessory mineral, in gneiss and schist, and in high-temperature veins and pegmatite dikes. Because it is highly resistant to chemical and physical weathering, it is common in placer deposits. Safflorite ... see loellingite Salt...sodium chloride...NaCl...see halite Comments Samarium...{suh-mair'-ee-uhm} Comments Sanidine ...potassium aluminum silicate...see feldspar Color: white to gray to yellow SG: 2.53 - 2.56 Comments: volcanic rock Sapphire Satin spar ... see gypsum Scapolite ...{skap'-oh-lyt} Crystallography: tetragonal Colors: pale yellow, colorless, pink chatoyant violet chatoyant Hardness: 6 Specific gravity: 2.7 Refractive index: avg, 1.57 v. .021 Occurrence: pale yellow from Brazil, chatoyant types are from Burma. Comments: Scapolite, a member of the feldspathoid group of minerals (sodium and calcium aluminosilicates), consists of a mixture of the minerals marialite and meionite. It occurs in calcium-rich metamorphic rocks, particularly schists, gneisses, and marbles. The name refers to the typical shaftlike shape of the prismatic, white crystals (tetragonal system). Hardness is 5 to 6, luster is vitreous, and specific gravity is 2.5 to 2.8. Some scapolite fluoresces yellow under ultraviolet light. Scheelite ...{sheel'-yt} Crystallography: tetragonal Colors: colorless, yellow, brown, green, white Luster: adamantine Hardness: 5 Specific gravity: 6.12 Refractive index: 1.918 - 1.934 Crystal or stone size: massive Comments: ore of tungsten, collector gem fluoresces strongly light blue under SW UV. Scheelite, calcium tungstate, is an ore mineral of tungsten. It forms pyramidal and tabular crystals (tetragonal system) and columnar or granular masses that vary in color from white through pale yellow. streak is white, luster is glossy, The fact that it fluoresces bright blue white under ultraviolet light enables prospectors to search for it at night, using portable "black" lights. It occurs in veins or pegmatites associated with granite or gneiss, and in contact metamorphic deposits. Schist...(sp) shist...{shist} a rock Comments Schorl... see tourmaline Scolecite... hydrated calcium aluminum silicate Crystallography: monoclinic Colors: colorless, white Luster: silky Hardness: 5 - 5.5 Specific gravity: 2.26 - 2.4 Comments: collector item Scorodite Selenite ... see gypsum Sepiolite ... meerschaum Color: white SG: 2 Hardness: 2 - 2.5 Comments: used in making pipes Serpentine...verd...williamsite... bowenite Crystallography: monoclinic Colors: yellowish green, green, black, white sometimes dyed Luster: greasy Hardness: 2.5 - 4; will.=4; bow.=5 - 5.5 Specific gravity: 2.57; bowenite = 2.8 Refractive index: normal 1.55 - 1.56...extreme 1.49 - 1.57 Crystal or stone size: massive Comments: used as jade sub. counters, walls The hydrous magnesium silicate mineral serpentine forms from the alteration of olivine and pyroxene in the presence of abundant water. Asbestos, its most fibrous form, is used as an insulating material. Serpentinite, the massive form of serpentine, may be cut and polished for ornamental stone. Serpentinite rocks are found associated with alpine peridotites and ophiolite sequences and are thought to be segments of altered mantle material that have been thrust upward into the Earth's crust. Siderite ... {sid'-ur-ite}...iron carbonate Crystallography: hexagonal Colors:yellow, brown, black Luster: vitreous Hardness: 3.5 - 4 Specific gravity: 3.7 - 3.9 Occurrence: The iron carbonate mineral siderite was formerly a major ore. It forms gray-to-brown rhombohedral crystals (hexagonal system) in silver-ore veins, compact concretions called clay ironstone in clay or shale deposits, and impure earthy material stratified with coal deposits called black-band ore. streak is white. Although black-band siderite ore has been mined, the most important ore deposits have been siderite replacements in limestones. good clear crystals are rare. Comments: crystals are of collector value Sillimanite...{sil'-uh-muhn-yt}...fibrolite Crystallography: orthorhombic Colors: gray, green, white, brown, grayish blue Hardness: 6 - 7 Specific gravity: 3.24 Refractive index: 1.64 - 1.68 Birefringence: .02 Crystal or stone size: massive Comments: The aluminum silicate mineral sillimanite, used in the manufacture of spark-plug porcelain and other refractories, has the same chemical formula, as andalusite and kyanite. Also called fibrolite because of its long, needlelike crystals (orthorhombic system) and fibrous masses, sillimanite has a vitreous luster and is brown to grayish. Sillimanite forms by the alteration of mica minerals in clayey sediments. Also an ornamental stone sub. for jade. Silver...Ag Color: silver SG: 10 - 12 Hardness: 2.5 - 3 Comments Simpsonite ... see microlite Skutterudite...cobalt arsenide Color: silverlike SG: 6.5 - 6.8 Hardness: 6 Comments: cobalt, nickel, and arsenic ore Smaltite ... skutterudite ... cobalt arsenide Crystallography: isometric Colors: gray to black Luster: metallic Hardness: 6 Specific gravity: 6.5 - 6.8 Comments: ore of cobalt, nickel, and arsenic Smithite... see miargyrite Smithsonite ... zinc carbonate Crystallography: hexagonal Colors: white, yellow, light green, blue Luster: greasy Hardness: 5 Specific gravity: 4.3 Cleavage: perfect rhombohedral Refractive index: 1.62 - 1.85 Birefringence: large Comments: The zinc carbonate mineral smithsonite is an ore of zinc, formed by oxidation of sphalerite. It occurs as rounded, crystalline crusts and granular or honeycombed masses that have a vitreous luster and are typically dirty brown or gray in color, and less often white or of a greenish or bluish hue. Streak is white. It is found with galena and sphalerite in veins and beds, especially in limestone regions.: uniaxial neg. sign. Soapstone ... see pyrophyllite, talc, steatite Sodalite ... sodium aluminum silicate chloride Crystallography: isometric Colors: blue, white, gray with green tints Luster: vitreous Hardness: 5.5 - 6 Specific gravity: 2.27 - 2.33 Cleavage: poor Refractive index: 1.48 Comments: used as sub. for lapis. Sodalite, a relatively rare sodium aluminosilicate, is one of the feldspathoid minerals. (Lazulite, a blue variety containing sulfur, is the principal component of lapis lazuli.) Sodalite forms dodecahedral crystals, embedded grains, and concentric nodules. Gray, greenish, yellowish, or white in color, it has a vitreous luster. It occurs with other feldspathoids in igneous rocks that have crystallized from sodium-rich magma. Soddyite... see gummite Soumansite... see wardite Spessartite...see garnet... spessartine Crystallography: cubic Colors: Red to brown, orange, pink Hardness: 6.5 - 7.5 Specific gravity: 4.2 Cleavage: none Refractive index: 1.79 - 1.81 Crystal or stone size: up to 10 cts. Comments: transparent are cut for gemstones Sphalerite...{sfal'-ur-yt}...zinc iron sulfide Crystallography: isometric Colors: yellow, reddish brown, black (marmatite) pink, green, colorless Luster: adamantine or resinous some iron rich varieties have submatallic luster Hardness: 3.5 - 4 Specific gravity: 3.9 - 4.2 Cleavage: perfect Comments: Sphalerite (ZnS), a common and widely distributed zinc sulfide mineral, is the major ore of zinc. Found in a variety of crystal forms as well as in cleavable, granular, or foliated masses, it ranges from colorless to brown and black in color, darkening as the amount of iron impurities increases. Streak is brownish, luster is resinous to adamantine, Sphalerite, usually in association with the lead sulfide galena, occurs in contact metamorphic deposits, in replacement deposits within limestone and dolomite, and in veins. Much is fluor. in UV Sphene Crystallography: monoclinic Colors: yellow, green, brown Hardness: 5.5 Specific gravity: 3.53 Refractive index: avg. 1.96 v. .12 Pleochroism: strong Comments: rare, large DR. dispersion higher than diamond. Sphene, also called titanite, is a titanium and calcium silicate mineral. When transparent and of good color, it is faceted to produce a brilliant, multicolored gem. Sphene forms wedge-shaped crystals (monoclinic system) of various forms and granular masses that range in color from brown to black through gray and green to yellow and red. Hardness is 5 to 5.5, luster is adamantine to resinous, and specific gravity is 3.4 to 3.6. Sphene occurs as an accessory mineral in igneous rocks, notably nepheline syenites, and in gneisses, schists, and marbles. Spinel...{spuh-nel'}...Ceyonite... gahnosspinel.(shades of blue); Balas Ruby is red spinel, flame, black, purple, yellow, greenish blue Comments: The magnesium aluminate mineral spinel is used as a GEM when transparent and finely colored. Ruby colored spinel has been confused with RUBY, the Black Prince's Ruby in the British Imperial State Crown being a famous example. The different colors of the mineral, caused by impurities, include various reds, yellow, blue, green, brown, and black, luster is vitreous. Gem spinels occur as crystals and pebbles in placer deposits, where they accumulate because they resist weathering. Common spinel occurs in metamorphic rocks and as an accessory mineral of some basic igneous rocks. Spodumene Subtypes: Hiddenite (yellow - green, green);Kunzite (pink-violet, violet) Crystallography: Monoclinic Luster: vitreous to glassy Hardness: 7 Specific gravity: 3.18 Cleavage: easy in two directions Refractive index: avg. 1.67 v. .015 Pleochroism: distinct Crystal or stone size: usually long crystals Comments: true green hiddenite very rare Staurolite ..{stohr'-uh-lyt} hydrous iron magnesium aluminum silicate .. Greek cross .. St.Andrew's cross Crystallography: orthorhombic Colors: gray to black brownish Luster: vitreous to resinous Hardness: 7 - 7.5 Specific gravity: 3.73 Occurrence: associated with garnet & kyanite Comments: The iron and magnesium aluminum silicate mineral staurolite forms well-developed, brown, prismatic crystals Twinned, cruciform pairs, in which one crystal penetrates another, are called fairy crosses and are worn as charms. The crystals often have a rough surface and subvitreous to resinous luster. Staurolite is typical of regional metamorphism, but less so of contact metamorphism. It is often associated with garnet and kyanite in crystalline schists and other altered clay-rich sediments. occurs in 90 & 60 degree angles. Seatite ... see talc .. soapstone .. pipe stone Stephanite ... silver antimony sulfide Crystallography: orthorhombic Colors: black Luster: metallic Hardness: 2 - 2.5 Specific gravity: 6.3 Comments: minor ore of silver Stibnite ... antimony sulfide Crystallography: orthorhombic Colors: gray, red (kermesite), yellow Luster: metallic iridescent Hardness: 2 Specific gravity: 4.6 - 4.7 Cleavage: perfect lengthwise Occurrence: Japan, US, Romania, China world wide Crystal or stone size: up to 18" long Comments: ore of antimony Stilbite ... hydrated sodium calcium aluminum silicate Crystallography: monoclinic Colors: white, gray, reddish brown Hardness: 3.5 - 4 Specific gravity: 2.1 Occurrence: US, Scotland, Canada, Brazil Comments: collector item Strontianite ... strontium carbonate Crystallography: orthorhombic Colors: white, pink, gray, green Luster: glassy Hardness: 3.5 - 4 Specific gravity: 3.7 Cleavage: good prismatic Occurrence: Germany, US, Scotland Crystal or stone size: compact fibrous masses Comments: ore of strontium, fireworks, glass Strontium Titanate ... man made ..strontianite is natural Crystallography: cubic (man made) Colors: all, colorless Hardness: 5.5 Specific gravity: 5.13 Refractive index: 2.41 Crystal or stone size: no more than 2.5 x 10 cm Comments: mfg. in 50's Sulphur Crystallography: orthorhombic Colors: yellow to brown to black Hardness: 1 Specific gravity: 2 - 2.1 Cleavage: poor Occurrence: crystals come from Sicily Comments: ore, mineral, S, sulfuric acid Syenite ... igneous rock {sy'-uh-nyt} Colors: gray, pinkish, violet Crystal or stone size: massive Comments: Syenite is a coarse-grained, intrusive igneous rock that is composed largely of sodium- or potassium-rich feldspar and of a ferromagnesian mineral. The feldspar commonly is orthoclase, albite, perthite, or, more rarely, microcline, and the dark-colored ferromagnesian mineral usually is biotite mica, hornblende, or a pyroxene; some examples of syenite also contain feldspathoid minerals. Syenite is in many respects similar to GRANITE; a major difference is the relative lack (less than 5%) or absence of quartz in syenite. Granite is much more commonly found in the field than is syenite. Sylvanite...{sil'-vuh-nyt} silver gold telluride Crystallography: monoclinic Colors: silvery white Luster: metallic Hardness: 1.5 - 2 Specific gravity: 8 - 8.3 Cleavage: perfect Comments: Sylvanite is a rare gold and silver telluride mineral. It forms brilliantly metallic prismatic or tabular crystals (monoclinic system), as well as imperfectly columnar to granular, cleavable masses. Hardness is 1.5 to 2, color and streak are steel gray to silver white, and specific gravity is 8.1. Sylvanite and the other tellurides (calaverite and krennerite) are mined from igneous rocks in the near-surface, low-temperature veins at Cripple Creek, Colo., and in the deeper-seated deposits at Kalgoorlie, Australia. Sylvite...{sil'-vyt}...potassium chloride Crystallography: isometric Colors: colorless, white, blue, yellowish red, purple Luster: vitreous Hardness: 2 Specific gravity: 1.99 Comments: fertilizer. The potassium chloride evaporite mineral sylvite (KCl) is mined as a source of potassium. It forms gray, white, or tinted cubic crystals (isometric system) and cleavable granular masses. Luster is vitreous, Sylvite occurs in basinlike bedded salt deposits. Taaffeite Crystallography: hexagonal Colors: pale red violet Hardness: 8 Specific gravity: 3.61 Refractive index: 1.719 - 1.723 Comments: neg. optic sign, collector gem Talc ... soapstone .. steatite ... hydrous magnesium silicate Crystallography: monoclinic Colors: white, greenish white, gray, brownish Luster: greasy Hardness: 1 to 2.5 Specific gravity: 2.58 - 2.83 Refractive index: 1.54 - 1.59 Crystal or stone size: massive Comments: used for carving, can be cut with knife. Talc is a common, extremely soft, basic magnesium silicate mineral; compact aggregates are known as soapstone (steatite) in reference to their soapy feel. Talc occurs as translucent, foliated or granular masses that vary in color from pale to dark green, with one perfect cleavage. Hardness is 1 (talc is a standard of hardness), streak is white, luster is pearly, and specific gravity is 2.7 to 2.8. Talc crystallizes in the monoclinic system. A low-grade metamorphic mineral, it forms when water and silica or carbon dioxide are added to extensively altered olivine- or pyroxene rich igneous rocks and when water and silica are added to altered carbonate rocks (with the release of carbon dioxide). Talc is also found in crystalline schists. In most instances, talc is found associated with carbonate minerals, particularly dolomite, and is associated frequently with tremolite, forsterite, and serpentine. Tanzanite... see zoisite Tarbuttite ... hydrous zinc phosphate Color: white, pink, yellow, and green SG: 4.1 Hardness: 3.7 Comments: collector item Tetrahedrite - tennantite group .. copper iron sulfide Color: purplish red or dark blue SG: 4.5 - 5.2 Hardness: 3 - 4.5 Comments: associated with copper, silver, lead, zinc silver ore. Thomsonite ... hydrated sodium calcium aluminum silicate Crystallography: orthorhombic Hardness: 5 - 5.5 SG: 2.3 - 2.4 RI: 1.515 - 1.54 Colors: white with brown impurities Crystal or stone size: crystals are rare Comments: usually cut in cabochon Thorianite ... thorium uranium oxide Color: gray to black SG: 9.7 - 9.8 Hardness: 6.5 Comments: ore of thorium and uranium Thulite ...see zoisite Tincalconite ... see borax Topaz ...an aluminum silicate mineral Topaz occurs in high-temperature veins, in pegmatites, and in granites and rhyolites, where it is one of the last minerals to form. Luster is vitreous. It has perfect cleavage in one direction. Common topaz is widespread, and fine gem material comes from Saxony, the Ural Mountains, Brazil, Japan, Mexico, and the Cairngorm Mountains in Scotland. Topazolite... see andradite Tourmaline ... {tur'-muh-leen} Subnames: Achroite (colorless); Rubelite (pink to red); Dravite (yellow brown to dark brown; Verelite (green); Indigolite /Indicolite (blue); Siberite (Lilac to violet blue); Schorl (black) Trachyte...{trak'-yt} Trachytes are volcanic rocks of intermediate silica and high alkali content. The lava flows from which they originate are usually quite viscous, and consequently they occur as short, thick flows, as tuffs, or as small dikes and sills. Feldspars are the major minerals found in trachytes. Either quartz or feldspathoids, but never both, may also occur, along with alkali-rich mafic minerals such as aegirine, augite, hornblende, and biotite. The lath shaped feldspar crystals are often aligned with the flow direction of the magma, giving rise to the typical trachytic texture. Trachytes are mineralogically and chemically similar to the coarser-grained syenites. Tremolite ... hydrous calcium magnesium silicate asbestos Color: white to greenish SG: 2.9 Hardness: 5 -6 Comments: asbestiform, serpentine, chrysotile forms used as asbestos Troilite... see pyrrhotite Troostite... see willemite Tsavorite ...grossular...see garnet Colors: green Occurrence: Kenya Crystal or stone size: over 1 ct. rare Comments: collector gem being found more and more in the trade. Tungstite... tungsten oxide + water... WO3.H2O Color: yellow earth colors Crystal system: orthorhombic Hardness: 2.5 SG: 5.5 Comments: rare Turnerite... see monazite Turquoise ...hydrous aluminum phosphate + copper... CuAl6(PO4)4(OH)8.4H2O Ulexite... hydrous sodium calcium borate... NaCaB5O9.8H2O Crystal system: triclinic Color: white Luster: silky Hardness: 2.5 SG: 1.6 Comments: desert borax deposits Uralite ... see hornblende Uranium ... Uraninite UO2... uranium dioxide crystal: cubic Color: black to gray, greenish Luster: submetallic to greasy Hardness: 5 - 6 Comments on Actinide elements Uranophane... hydrated calcium uranium silicate... CaU2Si2O11.7H2O Crystal system: rhombic Color: yellow to orange Luster: glassy Hardness: 2 - 3 SG: 3.8 - 3.9 Cleavage: pinacoidal Comments: fluorescent weak yellow green Uranotile... see uranophane Uvarovite ...see garnet... Ca3Cr2Si3O12 Crystal: cubic Colors: emerald green Luster: vitreous Hardness: 6.5 - 7.5 Specific gravity: 3.56 - 4.32 Cleavage: none Refractive index: 1.81 Occurrence: with olivine and chromite in peridotite of plutonic rocks and in serpentinite of hydrothermal metamorphic rocks. Comments: collector stone Vanadinite...{vuh-nay'-duh-nyt} lead vanadate chloride... Pb5(VO4)3Cl Crystal sys: hexagonal Color: red to yellow, brown to orange SG: 6.8 - 7.1 Hardness: 2.75 - 3 Comments: The uncommon lead vanadate mineral vanadinite is an ore of vanadium and a minor source of lead. It forms brown, yellow, or red barrel-shaped prismatic crystals (hexagonal system) in oxidized zones of lead deposits. Streak is white or pale yellow. Variscite ... hydrated phosphate of aluminum and strengite iron...Utahlite...vermiculite Crystallography: orthorhombic Colors:pale green to emerald green, bluish green, green, colorless, Luster: vitreous, waxy Hardness: 4 - 4.5 Specific gravity: 2.57 Cleavage: good in one direction Refractive index: 1.56 - 1.59 Occurrence: West U.S.A. World wide Crystal or stone size: usually nodules, sometimes confused with turquoise but it has a more green color and is lighter than turq. Comments: The name is from Variscia an ancient district in Germany where the mineral was first found. Crystals are rare but are cut as gemstones for collectors. Vesuvianite...hydrous calcium magnesium aluminum silicate... Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4 Crystal: ditetragonal Color: brown, olive green, yellow, red, blue SG: 3.27 - 3.45 Hardness: 6.5 Comments: crystals ejected by Vesuvius. Vivianite ... hydrated iron phosphate... Fe3(PO4)2.8H2O Crystal: monoclinic Color: blue to greenish black SG: 2.6 - 2.7 Hardness: 1.5 - 2 Comments: used as a coloring agent Volborthite ... hydrated copper vanadate Color: olive green SG: 3.5 - 3.8 Hardness: 3 Comments: collector item Wardite... hydrous sodium calcium aluminum phosphate... NaAl3(PO4)2(OH)4.2H2O Crystal system: tetragonal Color: bluish green to white Luster: glassy Hardness: 5 SG: 2.8 - 2.9 Fracture: conchoidal Cleavage: good basal Comments: Named for Henry A. Ward Wavellite ...{way'-vuh-lyt}... Al3(OH)3(PO4)2.5H2O...hydrous aluminum phosphate Color: white to green, yellow to brown SG: 2.4. Luster: glassy Hardness:3.25 to 4 Comments: The secondary, hydrated, aluminum phosphate mineral wavellite is widespread in small amounts associated with limonite and phosphate-rock deposits and with low-grade metamorphism. It forms white to green rounded crystalline aggregates. Luster is vitreous to resinous or pearly, streak is white, Whewellite ... calcium oxalate Color: white to colorless SG: 2.23 Hardness: 2.5 (unless you have one, then they are very hard.) Comments: one of the main components of kidney stones and urinary precipitates Willemite ... zinc silicate often with manganse and iron... Zn2SiO4 Crystallography: hexagonal Colors: yellow, green, red, brown, white, colorless. Luster: resinous to vitreous Hardness: 5.5 Specific gravity: 3.9 - 4.2 Cleavage: good in three directions Occurrence: associated w/calcite, franklinite, zincite Comments: strong fluorescent Witherite ... barium carbonite... BaCO3 Crystal: orthorhombic Color: colorless to gray, light yellowish, to white SG: 4.28 Luster: glassy Fracture: uneven, brittle Hardness: 3 - 3.75 Comments: barium ore Wollastonite... calcium silicate... CaSiO3 Crystal system: triclinic Color: white to colorless, pink or gray Luster: glassy to silky Hardness: 4.5 - 5 SG: 2.8 - 2.9 Fracture: splintery Cleavage: perfect pinacoidal on base Comments: often yellow to orange fluorescent used in the mfg. of refractories Wulfenite {wul'-fen-yt} stolzite, iron manganese tungstate... PbMoO4... wolframite Crystal sys: tetragonal Color: reddish brown, blackish brown, yellow SG: 6.5 -7 Hardness: 2.75 - 3 Comments: ore of tungsten. The lead molybdate mineral wulfenite is a minor ore of lead and molybdenum that occurs in the oxidized zone of lead deposits. It forms brilliant yellow, orange, and reddish, square, tabular crystals (tetragonal system) and granular masses. Streak is white, luster is resinous to adamantine. Xenotime ... see monazite YAG ... yttrium aluminum garnet Crystallography: cubic Colors: all Hardness: 8+ Specific gravity: 4.55 Refractive index: 1.83 Crystal or stone size: max. 4 x 20 centimeters Comments: man made Zincite...{zink'-yt}...zinc oxide Crystallography: hexagonal Colors: deep red to orange, yellow or brown Hardness: 4 Specific gravity: 5.4 - 5.7 Cleavage: perfect in one direction Refractive index: Occurrence: usually found with willemite and franklinite Comments: ore of zinc tinted with maganese. The zinc oxide mineral zincite (ZnO) is an important zinc ore found at Sterling Hill and Franklin, N.J., although it is rare elsewhere. It forms coarse grains and foliated masses that are orange yellow to deep red in color. Zircon...{zur'-kahn} Zoisite Enter content here Enter content here Enter content here |
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