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)2.10-12H2O 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)2.11H2O 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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