| Table 1
MINERALS WITH METALLIC TO SUBMETALLIC LUSTER |
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| Name | H | Color | Streak | Prominent Cleavage | Composition | Other Properties | |
| Molybdenite | 1 - 1.5 | Lead-gray | greenish to bluish gray | YES - 1 dir. (platy) | MoS2 | Greasy feel; flexible plates | |
| Graphite | 1 | steel-gray to black | gray to black | YES - 1 dir. (platy) | C | Greasy feel; flexible plates | |
| Covellite | 1.5 - 2 | indigo-blue | gray to black | YES - 1 dir. (platy) | CuS | Iridescent yellow and red | |
| Galena | 2.5 | Gray | gray | YES - 3 dir. at 90o | PbS | High specific gravity | |
| Chalcocite | 2.5 - 3 | black to lead gray | black to lead gray | NO | Cu2S | Brittle, high specific gravity | |
| Bornite | 3 | bronze, but with copper-red to purplish iridescence | grayish black | NO | Cu5FeS4 | Also known as peacock ore | |
| Chalcopyrite | 3.5 - 4 | brassy yellow, usually tarnished | greenish black | NO | CuFeS2 | Softer than pyrite; most common copper mineral | |
| Limonite (Goethite) | 4 - 5.5 | Yellow-brown, orange-brown, dark brown | yellowish brown to reddish | NO | Goethite: HFeO2 | Mixture of rust-like iron oxides. Mostly mineral "goethite." Earthy to metallic luster. Stalactitic, botryoidal forms common. | |
| Hematite | 5.5 - 6.5 | Steel-gray to reddish brown | reddish brown | NO | Fe2O3 | Most common iron mineral; specular hematite variety is composed of fine silvery flakes | |
| Magnetite | 5.5 - 6.5 | Black | black | NO (but sometimes shows parting) | Fe3O4 | Strongly magnetic; lodestone variety shows polarity; often in octahedral (8-sided) crystals | |
| Pyrite | 6 - 6.5 | Pale brassy yellow | greenish to brownish black | NO | FeS2 | Known as "Fool's Gold." Brittle, common in crystals, but also granular and massive (no obvious form). | |
|
MINERALS WITH NON-METALLIC LUSTER |
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| Name | H | Color | Streak | Luster | Prominent Cleavage | Composition | Other Properties |
| Talc | 1 | green, white, gray | white | pearly or greasy | YES - 1 dir. (Platy) | Mg3Si4010(OH)2 | Called "soapstone." Flexible plates, very soft |
| Sulfur | 1 - 2.5 | bright yellow | yellow | pearly | none | S | low melting temperature |
| Realgar | 1.5 - 2 | red to orange | orange-red | resinous | YES - 1 dir., GOOD | AsS | Sectile; yellow powder common on surface |
| Gypsum | 2 | colorless; white, gray, yellowish | white | vitreous | Only obvious in the selenite variety - 3 dir. (rhombic) | CaSO4.2H2O | 3 common varieties:
-selenite: clear, transparent -satin spar: fibrous, silky -alabaster: granular, sugary |
| Sylvite | 2 - 2.5 | Colorless, white, often reddish | white | vitreous | YES - 3 dir. at 90o | KCl | Bitter taste |
| Halite | 2.5 | Colorless, blue, yellow-blue | white | vitreous | YES - 3 dir. at 90o | NaCl | Salty taste, dissolves easily in water |
| Biotite Mica | 2.5 | Black, dark green, or brown | gray to white | vitreous or pearly | YES - 1 dir. (sheets) | K(Mg,Fe)3
(AlSi 3O10)(OH)2 |
Flexible and elastic sheets |
| Muscovite Mica | 2.5 | Colorless, gray, or green | white | vitreous | YES - 1 dir. (sheets) | Kal2(AlSi 3O10) (OH)2 | Flexible and elastic sheets |
| Bauxite | 2 - 7 | white to brown | white | earthy-dull | NO | Mixture of AlO(OH), Al(OH 3, and HAlO2 | Mixture of 3 clay minerals:
Boehmite, Gibbsite, and Diaspore. Earthy odor when breathed on. |
| Calcite | 3 | colorless or white; impurities may discolor it yellow or brown | white | vitreous | YES - 3 dir., not at 90o (rhombic) | CaCO3 | Effervesces vigorously with cold dilute hydrochloric acid. Transparent calcite shows double refraction. |
| Barite | 3 - 3.5 | Colorless, white; impurities may discolor it brown, red, or yellow | white | vitreous | YES - 2 dir. (seen in crystalline forms) | BaSO4 | High specific gravity (4.5). Ground-up barite is used as an weighting additive for drilling muds. |
| Dolomite | 3 - 3.5 | White, gray, brown, pink | white | vitreous to pearly | YES, but not always obvious (rhombic). | CaMg(CO3 ) 2 | Effervesces slowly with dilute cold hydrochloric acid, but only when powdered |
| Malachite | 3.5 - 4 | bright green | pale green | velvety, silky or dull | Not obvious in rock masses | Cu2(CO3)(OH)2 | Effervesces in hydrochloric acid. Frequently in banded, botryoidal masses. Flame test produces green color. |
| Sphalerite | 3.5 - 4 | dark brown or black to yellow | light yellow to brown | resinous to sub-metallic | YES - 6 dir. (all 6 directions not always obvious) | ZnS | Reacts with hydrochloric acid only when powdered to produce hydrogen sulfide gas. |
| Fluorite | 4 | colorless, white, yellow, purple, blue, green | white | vitreous | YES - 4 dir. (all 4 directions not always obvious) | CaF2 | Cubic crystals common, 8-sided diamond-shaped crystals sometimes seen; often fluorescent |
| Apatite | 5 | shades of yellow, green, blue, brown | white | vitreous | Not obvious - indistinct | Ca5(PO4) 3
(F,Cl,OH) |
Commonly seen as 6-sided prismatic crystals |
| Limonite (Goethite) | 4 - 5.5 | Yellow-brown, orange-brown, dark brown | yellowish brown to reddish | earthy, dull | NO | Goethite: HfeO2 | Ordinary "rust" - a mixture of iron oxides, composed mostly of goethite. |
| Hematite | 5.5.- 6.5 | Red and reddish brown | reddish brown | dull to sub-metallic | NO | Fe2O3 | Commonly appears in these forms: oolitic, botryoidal, or massive (no obvious form) |
| Augite (pyroxene) | 6 | dark green to black | gray | vitreous | YES - 2 dir. at nearly 90o | complex silicate | Most common pyroxene; often appears as short, stubby, prismatic crystals in rock. |
| Hornblende (amphibole) | 6 | black, dark green, or brown | grayish-white | vitreous | YES - 2 directions, ith angles at 56o and 24o | complex silicate | Most common amphibole; found in many igneous rocks. Characterized by dark, elongated crystals |
| Olivine | 6 | olive green or brownish | white or gray | vitreous to adamantine | Not obvious - indistinct | (Mg,Fe) 2 SiO4 | Often found as "sugary" granular masses of dunite (olivine rock); gem variety called peridot |
| Plagioclase feldspar
(including Albite, Labradorite, etc.) |
6 | white to dark gray | colorless or white | vitreous | YES - 2 dir. at nearly 90o | NaAlSi3O8 to
CaAlSi2O8 |
Sodium-rich varieties are white or light gray; calcium-rich varieties are medium to dark gray. Labradorite variety shows blue play of colors. |
| Potassium feldspar
(Orthoclase, Microcline) |
6 | white, tan to orange, red, green, also colorless | colorless or white | vitreous or pearly | YES - 2 dir. at nearly 90o | KAlSi3O8 | Most commonly found in granites and pegmatites. |
| Quartz
(crystalline varieties) |
7 | colorless, white, gray, purple, pink, black, yellow, green | colorless | vitreous | NO - shows conchoidal fracture | SiO2 | Varieties named by color:
Rock crystal (colorless), Milky (white), Smoky (gray), Amethyst (purple), Rose (pink), Citrine (yellow); 6-sided crystals common |
| Silica
(Chalcedony varieties) |
7 | all colors observed | colorless | waxy or dull usually | NO - conchoidal fracture predominant | SiO2 | Collectively called "chalcedony" Agate (banded), Jasper (red or brown), Chert or Flint (white, gray or black) |
| Garnet group
(Almandine, etc.) |
7 - 7.5 | commonly red and brown; also yellow, pink, green, black | colorless to pale brown | vitreous or resinous | NO - but sometimes shows parting | silicates of Al, Ca, Mg, Ge, Mn, Cr | Commonly found in metamorphic rocks (transformed from plagioclase); 12-sided (dodeca-hedral) crystals are common |
| Tourmaline | 7 - 7.5 | black; also green, pink, brown | colorless | vitreous | Not obvious - indistinct | complex silicate of B, Al, Fe, Mg | Common in 3-sided crystals, often prismatic with striations or columnar structure |
| Corundum | 9 | gray, brown, blue, red, colorless | colorless | dull, vitreous, adamantine | NO - but common shows parting | Al2O3 | Often in barrel-shaped crystals.
Clear gem varieties include: -sapphire(blue) -ruby (red) -emerald (green) Granular form is called emery |