Mineral Identification Key

The Mineral Identification Key

Copper, Michigan, Seaman Museum specimen

Table IIC-2b: Nonmetallic Luster; Streak Not Colored; Hardness 2½ to 3; Cleavage Not Prominent; Infusible in a Candle Flame. [Previous Table] [Next Table]

Color Hardness Luster Name System Habit SG Notes

White to Tan, may be Greyish 2 to 2½ Earthy KAOLINITE
Al₂Si₂O₅(OH)₄ Triclinic Usually as compact earthy masses 2.6 Has an earth odor when moistened, sticks to a dry tongue

Colorless to White or Greyish-white, may be tinted other colors 3 to 3½ Vitreous and/or pearly ANHYDRITE
CaSO₄ Orthorhombic Usually in coarsely crystalline masses exhibiting a pseudo-cubic cleavage, or in granular masses with no cleavage apparent, crystals rare and usually equant or thick tabular 2.9 to 2.98 Pseudo-cubic cleavage

Colorless to White or Greyish-white, may be tinted other colors 3 to 3½ Vitreous to sub-vitreous WITHERITE
(Aragonite Group):
BaCO₃ Orthorhombic, pseudo-
hexagonal Usually as stout prismatic twinned crystals with a hexagonal cross section, often with pyramidal terminations on both ends, more rarely as globular to botryoidal clusters, coarse fibrous aggregates, and granular 4.29 Often hazed, will effervesce in cold acid. Has cleavage, but it may not be seen.

Colorless to White or Grey, may be tinted other colors 3½ to 4 Vitreous to sub-vitreous, silky when fibrous STRONTIANITE
(Aragonite Group)
SrCO₃ Orthorhombic Usually in granular or fibrous aggregates, may be columnar, crystals short prismatic to acicular, often pseudo-hexagonal in cross- section (Ca-rich) 3.76 Effervesces mildly in cold acids, or not at all. Distinguished from cerussite by its notably lower specific gravity, lighter feel. Also it is not as common as cerussite.

Shades of Green - olive, apple, dark to blackish, often mottled 2½ to 4; rarely 5 to 6 in dense massive material Sub-vitreous to greasy luster, feels greasy ANTIGORITE/
LIZARDITE/AMESITE
(Serpentine Group)
(Fe,Mg)₃(Si,Al)₂O₅(OH)₄Mg₃(Si,Al)₂O₅(OH)₄Mg₂Al(Si,Al)₂O₅(OH)₄ Monoclinic, Orthorhombic and Triclinic Usually in crystalline masses, often platy or columnar 2.4 to 2.79 (antigorite), 2.55 to 2.61 (lizardite), 2.71 to 2.80 (amesite) These serpentine minerals are almost impossible to tell apart, particularly in massive forms. They may co-exist at the same locality. Still, information on the specific locality a specimen comes from may be the best bet for nailing down the ID.

White to Grey, Pale-green to Olive-green, Golden-yellow to Brown 2 to 3 Silky CLINOCHRYSOTILE/
ORHTOCRYSOTILE/
PARACHRYSOTILE (Serpentine Group): Mg₃Si₂O₅(OH)₄ Monoclinic &
Orthorhombic Usually in fine fibrous aggregates,
fibers often very long and "weaveable," 2.53 to 1.55 "Asbestos" is an industrial term for several long-fiber species (not all Serpentines) that can be made into cloth or mats.
These species are extremely difficult to tell apart, although parachrysotile is rare and not likely to be seen. Most specimens are simply labeled with the generic term: CHRYSOTILE

Orange-red to Ruby-red, Brownish-red to Brownish-yellow or Pale
Straw-yellow 2½ to 3 Sub-vitreous to sub-resinous 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 Streak white, may be yellowish

Dark-green to Yellow-green, Yellow to Orange-Yellow, Brown, White, even Colorless 3½ Sub-vitreous to resinous PYROMORPHITE
(Apatite Group):
Pb₅(PO₄)₃Cl Hexagonal Usually in barrel- shaped, prismatic hexagonal crystals, may also be spindle- shaped, hollow – "hopper crystals"; – rarely tabular or pyramidal, crystals may exhibit concentric color or structural zones due to zoned variations in composition 7.04 White streak; difficult to distinguish from mimetite without tests for PO₄ vs. AsO₄.

Pale-yellow to Yellowish-brown, Orange-yellow to Orange-red, White
to Colorless 3½ to 4 Sub-vitreous to resinous MIMETITE
(Apatite Group):
Pb₅(AsO₄)₃Cl Hexagonal Usually in simple barrel-shaped prismatic crystals, rarely tabular or acicular, may be botryoidal or globular 7.28 Difficult to distinguish from pyromorphite without tests for AsO₄ vs. PO₄; Named for the fact that it closely mimics pyromorphite

Green to Yellow, Greenish-white, Yellowish-brown to Brown, rarely other hues 3½ to 4 Vitreous to
pearly, sometimes resinous WAVELLITE
Al₃(PO₄)₂(OH,F)₃^.5H₂O Orthorhombic Usually in radiating fibrous aggregates or stellate clusters, as crusts, may be stalactic 2.36 Streak white; one perfect and one distinct cleavage, but they are rarely seen, dissolves in cold acids.

Note: The above three members of the Apatite Group are difficult to tell apart when they have the color(s) of vanadinite, though usually the colors in vanadinite are deeper, more intense, than the other two. Vanadinite has lower S.G. than the other two as well.
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Color	Hardness	Luster	Name	System	Habit	SG	Notes
White to Tan, may be Greyish	2 to 2½	Earthy	KAOLINITE Al₂Si₂O₅(OH)₄	Triclinic	Usually as compact earthy masses	2.6	Has an earth odor when moistened, sticks to a dry tongue
Colorless to White or Greyish-white, may be tinted other colors	3 to 3½	Vitreous and/or pearly	ANHYDRITE CaSO₄	Orthorhombic	Usually in coarsely crystalline masses exhibiting a pseudo-cubic cleavage, or in granular masses with no cleavage apparent, crystals rare and usually equant or thick tabular	2.9 to 2.98	Pseudo-cubic cleavage
Colorless to White or Greyish-white, may be tinted other colors	3 to 3½	Vitreous to sub-vitreous	WITHERITE (Aragonite Group): BaCO₃	Orthorhombic, pseudo- hexagonal	Usually as stout prismatic twinned crystals with a hexagonal cross section, often with pyramidal terminations on both ends, more rarely as globular to botryoidal clusters, coarse fibrous aggregates, and granular	4.29	Often hazed, will effervesce in cold acid. Has cleavage, but it may not be seen.
Colorless to White or Grey, may be tinted other colors	3½ to 4	Vitreous to sub-vitreous, silky when fibrous	STRONTIANITE (Aragonite Group) SrCO₃	Orthorhombic	Usually in granular or fibrous aggregates, may be columnar, crystals short prismatic to acicular, often pseudo-hexagonal in cross- section (Ca-rich)	3.76	Effervesces mildly in cold acids, or not at all. Distinguished from cerussite by its notably lower specific gravity, lighter feel. Also it is not as common as cerussite.
Shades of Green - olive, apple, dark to blackish, often mottled	2½ to 4; rarely 5 to 6 in dense massive material	Sub-vitreous to greasy luster, feels greasy	ANTIGORITE/ LIZARDITE/AMESITE (Serpentine Group) (Fe,Mg)₃(Si,Al)₂O₅(OH)₄Mg₃(Si,Al)₂O₅(OH)₄Mg₂Al(Si,Al)₂O₅(OH)₄	Monoclinic, Orthorhombic and Triclinic	Usually in crystalline masses, often platy or columnar	2.4 to 2.79 (antigorite), 2.55 to 2.61 (lizardite), 2.71 to 2.80 (amesite)	These serpentine minerals are almost impossible to tell apart, particularly in massive forms. They may co-exist at the same locality. Still, information on the specific locality a specimen comes from may be the best bet for nailing down the ID.
White to Grey, Pale-green to Olive-green, Golden-yellow to Brown	2 to 3	Silky	CLINOCHRYSOTILE/ ORHTOCRYSOTILE/ PARACHRYSOTILE (Serpentine Group): Mg₃Si₂O₅(OH)₄	Monoclinic & Orthorhombic	Usually in fine fibrous aggregates, fibers often very long and "weaveable,"	2.53 to 1.55	"Asbestos" is an industrial term for several long-fiber species (not all Serpentines) that can be made into cloth or mats. These species are extremely difficult to tell apart, although parachrysotile is rare and not likely to be seen. Most specimens are simply labeled with the generic term: CHRYSOTILE
Orange-red to Ruby-red, Brownish-red to Brownish-yellow or Pale Straw-yellow	2½ to 3	Sub-vitreous to sub-resinous	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	Streak white, may be yellowish
Dark-green to Yellow-green, Yellow to Orange-Yellow, Brown, White, even Colorless	3½	Sub-vitreous to resinous	PYROMORPHITE (Apatite Group): Pb₅(PO₄)₃Cl	Hexagonal	Usually in barrel- shaped, prismatic hexagonal crystals, may also be spindle- shaped, hollow – "hopper crystals"; – rarely tabular or pyramidal, crystals may exhibit concentric color or structural zones due to zoned variations in composition	7.04	White streak; difficult to distinguish from mimetite without tests for PO₄ vs. AsO₄.
Pale-yellow to Yellowish-brown, Orange-yellow to Orange-red, White to Colorless	3½ to 4	Sub-vitreous to resinous	MIMETITE (Apatite Group): Pb₅(AsO₄)₃Cl	Hexagonal	Usually in simple barrel-shaped prismatic crystals, rarely tabular or acicular, may be botryoidal or globular	7.28	Difficult to distinguish from pyromorphite without tests for AsO₄ vs. PO₄; Named for the fact that it closely mimics pyromorphite
Green to Yellow, Greenish-white, Yellowish-brown to Brown, rarely other hues	3½ to 4	Vitreous to pearly, sometimes resinous	WAVELLITE Al₃(PO₄)₂(OH,F)₃^.5H₂O	Orthorhombic	Usually in radiating fibrous aggregates or stellate clusters, as crusts, may be stalactic	2.36	Streak white; one perfect and one distinct cleavage, but they are rarely seen, dissolves in cold acids.