The Mineral Identification Key |
Table IIA: Minerals with a Nonmetallic Luster, Definitely Colored Streak, and Hardness 1 to 6 [Previous Table] [Next Table]
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Rust-red to Indian-red | 1+ to 6½ | Dark-brown to Steel-grey to Black | HEMATITE Fe2O3 |
Trigonal | Usually massive in radiating, reniform, or micaceous aggregates | 4.8 to 5.3 | Hardness and S.G. lower in earthy massive materials, harder and denser in crystals and crystalline materials, crystals usually 5½ to 6½ with a metallic to sub-metallic luster | |
Pink | 1½ to 2½ | Pale-pink to Red | Perfect in one direction | ERYTHRITE Co3(AsO4)2.8H2O |
Monoclinic | Usually as earthy crusts or powdery coatings on cobalt minerals, may be reniform | 2.95 | Streak same color as the sample but paler. Rare. (See also annabergite, below.) |
Pale-pink to Light-green | 1½ to 2½ | Apple-green , Grey, Pale-rose | Perfect in one direction | ANNABERGITE Ni3(AsO4)2.8H2O |
Monoclinic | Usually as coatings or crusts of tiny crystals, grainy-appearing, crystals bladed | 3.0 to 3.23 | Streak same color as sample but lighter; Rare. (See also erythrite above.) |
Red | 2 | Red | LITHARGE PbO |
Tetragonal | As alteration crusts on massicot (see below) | 9.14 | Rare | |
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Bright-Scarlet-red or Vermilion to Brownish-red | 2 to 2½ | Dark Ruby- red or Bright Ruby-red |
One distinct direction | PROUSTITE/ PYRARGYRITE Ag3(Sb,As)S3 Ag3(As,Sb)S3 |
Trigonal | Prismatic, pyramidal, rhombohedral, and scalenohedral crystals , also massive, usually as complex intergrown crystal aggregates | 5.58 (pyrargyrite) 5.57 (proustite) |
Isostructural species difficult to distinguish, though pyrargyrite is usually darker in color and more common than proustite, fusible in candle flame. Rare. |
Dark-red | 2½ | Dark-red to Vermilion | One perfect direction | CINNABAR HgS |
Trigonal | Usually earthy or granular, commonly impure and dark red or reddish-brown, bright-red and translucent to transparent when pure, crystals rhombohedral or tabular to short prismatic | 8.10 | Luster of crystals adamantine, may appear sub-metallic, heavy |
Bright- to Deep-red | 2½ to 3 | Orange-yellow | One distinct direction | CROCOITE PbCrO4 |
Monoclinic | Usually in prismatic crystals with an adamantine to sub-vitreous luster, as parallel to jackstraw clusters, may be hollow | 5.9 to 6.1 | Decrepitates (crumbles explosively) in a candle flame |
Dark-red | 3½ to 4 | Ruby-red to Reddish-brown | CUPRITE Cu2O |
Isometric | Usually in octahedral or cubic crystals, may be in slender crystals, may also be massive | 6.0 | ||
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Orange-or Reddish-yellow | 1½ to 2 | Dark-red | One good direction | REALGAR AsS |
Monoclinic | Usually massive, granular, coarse to fine, and as crusts | 3.48 | Luster resinous, easily fusible in a candle flame; usually associated with Orpiment |
Orange-yellow | 4 to 4½ | Yellow to Orange-yellow to Deep-red |
One perfect direction |
ZINCITE (Zn,Mn)O |
Hexagonal | Usually massive as irregular grains or rounded masses | 5.64 to 5.68 | Luster sub-adamantine to sub-vitreous, fluoresces green to yellowish-green under long wave ultraviolet light. Rare outside of Franklin, N.J., USA. |
Pale-yellow | 1½ to 2½ | Lemon-yellow | One perfect direction giving thin plates |
ORPIMENT As2S3 |
Monoclinic | Usually in foliated masses or grains | 3.49 | Flexible, luster resinous, pearly on cleavage surfaces, easily fusible in a candle flame, usually associated with Realgar |
Pale-yellow | 1½ to 2½ | Bright-yellow | Imperfect in three directions | SULFUR S |
Orthorhombic | Usually imperfectly crystallized masses or crusts | 2.05 to 2.09 | Resinous to sub-vitreous luster, may appear somewhat earthy when massive or as crusts, readily burns in a candle flame giving a blue flame. |
Pale-yellow | 2 | Sulfur-yellow | MASSICOT PbO |
Orthorhombic | Usually earthy or scaly masses | 9.56 | Usually replaces other Pb minerals, particularly galena, scales flexible. Rather rare. | |
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Very Pale-yellow to Yellowish-green | 2 to 2½ | Lemon-yellow to Greenish-yellow | One perfect direction and one distinct direction | AUTUNITE/ META-AUTUNITE Ca(UO2)2(PO4)2.2-6H2O |
Tetragonal/ Orthorhombic |
Usually as micaceous or scaly foliated aggregates, crystals thin or thick tabular | 3.15 (autunite), 3.44 (meta-autunite) | Luster vitreous to adamantine, fluoresces bright greenish-yellow. (See also torbernite/metatorbernite below, does not fluoresce.) Naturally occurring material is almost invariably meta-autunite |
Very Pale-yellow, Yellowish-white (both rarely seen), White | 2½ to 3 | Orange-red to Ruby-red, Brownish-red to Brownish-yellow or Pale Straw-yellow | VANADINITE (Apatite Group) Pb5(VO4)3Cl |
Hexagonal | Usually in barrel-shaped prismatic hexagonal crystals, either long or short, may be acicular in clusters or mats ("endlichite"), and as hollow prisms "hopper" crystals | 6.88 | Luster sub-vitreous to sub-resinous | |
Very Pale-green | 2 to 2½ | Emerald- to Grass-green, Apple-green, Leek-green | One perfect direction and one indistinct direction | TORBERNITE/
METATORBERNITE Cu(UO2)2(PO4)2.8H2O |
Tetragonal | Usually as micaceous or scaly foliated aggregates, crystals thin to thick tabular | 3.22 (torbernite), 3.70 (metatorbernite) |
Luster vitreous to adamantine, similar to autunite/meta-autunite but truly green and does not fluoresce like autunite/meta-autunite. (See also autunite/ meta-autunite above.) Naturally occurring material is almost always metatorbernite |
Light-green | 3 to 3½ |
Dark to Bright Emerald-green | One perfect direction, a second fair direction | ATACAMITE Cu2Cl(OH)3 |
Orthorhombic | Usually in granular cleavable masses, crystals prismatic and usually very small to microscopic | 3.75 to 3.77 | Fusible in a candle flame. Rare. |
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Light-green | 3½ | Dark Emerald-green | One perfect direction, one poor direction | ANTLERITE Cu3(SO4)(OH)4 |
Orthorhombic | Usually as mats of tiny acicular crystals, may be granular | 3.88 | Vitreous luster, may appear sub-vitreous or dull in mats. Rare. |
Light-green | 3½ to 4 | Dark Emerald-green to Bright-green | BROCHANTITE Cu4(SO4)(OH)6 |
Monoclinic | Usually as crusts or mats of tiny crystals, crystals may be stout prismatic to acicular or tabular | 3.97 | Vitreous luster | |
Light-green | 3½ to 4 | Dark- to Bright-green | One perfect direction | MALACHITE Cu2(CO3)(OH)2 |
Monoclinic | As either radiating fibrous masses, botryoidal to mammillary, or as slender to stout prismatic crystals, often poorly formed (and often psuedomorphic after azurite), may be crusts, or acicular stellate sprays | 3.9 to 4.03 | Luster adamantine to vitreous, may appear sub-vitreous to dull on surfaces of masses. Often associated with azurite |
Pale Bluish-white to White or Colorless | 1½ to 2 | Deep-blue or Deep Greenish-blue to Bluish green | One perfect direction | VIVIANITE Fe3(PO4)2.8H2O |
Monoclinic | Usually as flattened to bladed prismatic crystals, often in stellate clusters or sprays, may also be granular, crusts, or reniform masses | 2.68 | Streak: darkens to Dark-blue or Brown after exposure, vitreous luster. Rare |
Very Pale-blue to Grey or Tan | 2 to 4 | Pale- to Deep-blue, Blue-green, Green | CHRYSOCOLLA Cu2H2[Si2O5](OH)4 |
Usually in glassy, opaline, or porcellaneous masses or crusts, often as mats of very fine acicular crystals, may be botryoidal | 1.93 to 2.40 | Luster may be vitreous, waxy, porcellaneous, or dull. | ||
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Light-blue | 2½ | Azure-blue to Bright-blue | LINARITE PbCu(SO4)(OH)2 |
Monoclinic | Usually as clusters or sprays of tiny elongated prismatic or tabular crystals, bladed, may also be in crusts of crudely formed crystals | 5.35 | Luster vitreous to sub-adamantine, easily fusible in a candle flame | |
Light-blue | 3½ to 4 | Deep Azure-blue | One perfect direction | AZURITE Cu3(CO3)2(OH)2 |
Monoclinic | Usually as small stout prismatic crystals, may be in sprays or radiating spherical groups | 3.77 | Luster vitreous, may appear sub-vitreous to dull on surfaces of radiating spherical masses; usually associated with malachite |
Bright-blue | 5 to 5½ | Deep-blue to Medium-blue and Violet-blue | One distinct direction | LAZURITE Na3Ca(Al3Si3O12)S |
Isometric | Usually massive, compact to granular, crystals rare, dodecahedral | 2.38 to 2.45 | Luster vitreous in crystals, dull in massive material. Rare. Principal mineral found in the gem stone Lapis Lazuli |
Very Pale-blue to White | 5½ to 6 | Light- to Medium-blue, Violet-blue, Grey, or White |
One poor to distinct direction | SODALITE Na4(Al3Si3O12)Cl |
Isometric | Usually massive granular, crystals rare, dodecahedral, octahedral. Rare | 2.14 to 2.30 | Luster vitreous in crystals to dull in massive material, may fluoresce orange to orange-red |
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Brown | 3½ to 4 | Light-tan to Dark-brown | Perfect in three directions producing rhombic fragments | SIDERITE FeCO3 |
Trigonal | Usually in cleavable masses, crystals usually rhombohedrons, faces curved | 3.83 to 3.88 | Becomes magnetic when heated in a candle flame |
Brown | 3½ to 4 | Dark-brown to Black | One perfect direction | FERBERITE/ HÜBNERITE ("Wolframite" series) (Fe,Mn)WO4 (Mn,Fe)WO4 |
Monoclinic | Usually massive, granular, crystals tabular to bladed with vertical striations | 7.0 to 7.5 S.G. above 7.3 indicates ferberite, lower indicates hübnerite |
Color black in ferberite, brown in hübnerite. Streak darkens with increasing Fe content |
Light-brown | 3½ to 4 | Dark to Light-brown, Olive-brown, Reddish brown, Reddish-black | Perfect in six directions | SPHALERITE ZnS |
Isometric | Usually in cleavable masses, granular, crystals blocky wedge-shaped | 3.9 to 4.1 | May have an oily, submetallic, luster, streak usually lighter than the specimen |
Streak | Hardness | Color | Cleavage | Name | System | Habit | SG | Notes |
Yellow-brown to Ocher-yellow | 5 to 5½ | Dark-brown to Black | One perfect direction | GOETHITE (pronounced "Ger-ta-ite") FeO(OH) |
Orthorhombic | Usually in reniform or radiating fibrous masses, botryoidal or mammillary, also stalactic | 4.4 | Luster usually dull, may be submetallic. |
Light-brown | 6 to 6½ | Reddish-brown to Black | One distinct direction | RUTILE TiO2
|
Tetragonal | Usually in slender prismatic crystals with vertically striated faces, as "elbow twins" (reticulated) and "sixlings" | 4.18 to 4.25 | Luster adamantine, may appear submetallic, usually translucent |
Brown to Black | 6 to 7 | Light-brown to Greyish or White | One imperfect direction | CASSITERITE SnO2 |
Tetragonal | Usually as fibrous, reniform, or irregular masses, stream-worn nuggets, with a dull to submetallic luster, crystals usually twined, with a submetallic or adamantine luster | 6.8 to 7.1 | Streak usually lighter than the specimen |
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