Mineral Identification Key

The Mineral Identification Key

Copper, Michigan, Seaman Museum specimen

Table IB: Minerals with Metallic or Submetallic Luster & Hardness greater than 2½, but less than 5½: (Will not easily mark paper, but can be scratched with a pocket knife.) [Previous Table] [Next Table]

Hardness Color Streak Cleavage Name System Habit SG Notes

1 to 2 Iron-black Black One perfect direction PYROLUSITE
MnO₂ Tetragonal May be splintery or in radiating fibrous masses 4.7 Will sometimes mark paper.

1½ to 2 Silvery-white Grey SYLVANITE
(Au,Ag)Te₂ Monoclinic Usually granular or in bladed aggregates, often appears as skeletal forms on rocks, resembling writing (cuneiform) 8 to
8.2 May mark paper.
Rare

1½ to 2 Metallic-blue, tarnishes to blue-black Black One perfect direction (basal) COVELLITE
CuS Trigonal Platy masses or thin six-sided platy crystals 4.6 May be somewhat iridescent, turns metallic-purple when wet. Will sometimes mark paper.

Hardness Color Streak Cleavage Name System Habit SG Notes

2 Bluish-black to Silvery-black Grey-black One perfect direction (prismatic), two imperfect STIBNITE
Sb₂S₃ Orthorhombic Usually as thick bladed crystals with striations both parallel to and across the long axis; crystals often bent or "kinked" 4.5 Fuses in a candle flame. Will sometimes mark paper.

2 to 2½ Deep Ruby-red to Bright Ruby-red Brownish-red to Scarlet or Vermilion One distinct direction PYRARGYRITE/ PROUSTITE
Ag₃(Sb,As)S₃Ag₃(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 a candle flame. Rare.

2 to 2½ Grey-black to Lead-grey Black ACANTHITE
Ag₂S Isometric Pseudo-cubic, usually massive 7.3 Bright steel-grey on fresh surfaces but darkens upon exposure, easily cut with a knife (sectile). Will usually mark paper.

Hardness Color Streak Cleavage Name System Habit SG Notes

2½ Bluish-black to Lead-grey Grey-Black to Black Perfect in three directions at 90^o to each other GALENA
PbS Isometric Usually in cubic crystals or masses exhibiting cubic cleavage, also in granular masses 7.6 Will usually mark paper. Most common heavy mineral.

2½ Brass-yellow to Silvery-white Yellowish to Greenish-grey CALAVERITE
AuTe₂ Monoclinic Usually granular, rarely in distinct elongated crystals 9.35 Very heavy, easily fusible in a candle flame (leaving globules of gold). May mark paper. Rare.

2 to 3 Grey-black Black One good direction JAMESONITE
Pb₄FeSb₆S₁₄ Monoclinic Dense clusters or carpets of fibrous to acicular crystals; very delicate! 5.5 to 6.0 Fuses easily in a candle flame.

Hardness Color Streak Cleavage Name System Habit SG Notes

2½ to 3 Grey-black Grey to Black BOURNONITE
PbCuSbS₃ Orthorhombic Usually in stout prismatic crystals often as intergrown clusters with twinning exhibited by re-entrant angles 5.8 to 5.9 Fuses easily in a candle flame

2½ to 3 Steel-grey, may tarnish to black on exposure Grey to Black CHALCOCITE
Cu₂S Monoclinic, pseudo-
orthorhombic Usually in compact masses, crystals tabular to stoutly prismatic, often with a pseudo-hexagonal outline, vertically striated. 5.7

2½ to 3 Dark metallic Blue to Black Black DIGENITE
Cu₉S₅ Isometric Usually massive as small to tiny irregular grains, very rarely as octahedral crystals 5.5 to 5.7 Very similar to chalcocite, but much rarer in non-microscopic sizes.

2½ to 3 Steel-grey, tarnishes metallic blue Dark steel-grey STROMEYERITE
AgCuS Orthorhombic, pseudo-
hexagonal Usually massive, granular, rarely as pseudo-hexagonal prismatic crystals 6.2 to 6.3 Rare.

Hardness Color Streak Cleavage Name System Habit SG Notes

2½ to 3 Lead-grey Brown to brownish-grey One distinct direction BOULANGERITE
Pb₅Sb₄S₁₁ Monoclinic Usually massive as fibrous bundles, crystals usually needle-like mats, prismatic crystals rarer 6.0 to 6.3 Thin acicular crystals flexible. Rare.

2½ to 3 Dark-red to Vermilion Dark-red One perfect direction CINNABAR
HgS Trigonal Usually massive, crystals uncommon and usually rhombohedral, often as penetration twins 8.10 Luster actually adamantine, appearing metallic, heavy.

2½ to 3 Copper-red on fresh surfaces, tarnishes to brown or black Coppery-red, shiny COPPER
Cu Isometric Usually in irregular masses, large grains, wires, and crude dendritic crystals, crystals usually octahedral and malformed, may be cubic or other Isometric forms 8.9 Malleable.

2½ to 3 Golden-yellow, shiny, becoming paler with increased Ag content - electrum variety Golden-yellow, shiny GOLD
Au Isometric Usually massive in irregular grains, nuggets, "leaves" and "flakes", crystals often wires crudely dendritic or as malformed octahedrons 15.0 to 19.3 Malleable, very heavy! Rare. Distinguished from pyrite – "fools gold" – by its malleability, softness and weight.

2½ to 3 Silvery-white,
tarnishes black Silvery-white, shiny SILVER
Ag Isometric Usually massive as irregular grains, wires, and dendritic crystals 10.5 Malleable, heavy. Rare. May mark paper.

Hardness Color Streak Cleavage Name System Habit SG Notes

3 Grey-black Black One perfect (prismatic), two distinct, and one indistinct direction ENARGITE
Cu₃AsS₄ Orthorhombic Usually in bladed masses 4.4 Crystals vertically striated

3 Brownish-bronze on fresh surfaces, tarnishing to metallic purple, iridescent ("peacock ore") Grey-black BORNITE
Cu₅FeS₄ Orthorhombic,
pseudo-
tetrahedral Crystals usually pseudo-cubic, usually massive 5.1 Thin splinters fusible in a candle flame, giving a brittle magnetic globule.

3 to 3½ Brass-yellow Black, sometimes with a greenish tinge MILLERITE
NiS Trigonal Usually in radiating groups or mats of needle-like to hair-like crystals 5.5 Slender crystals usually have a greenish tinge

3 to 3½ Steel-grey Steel-grey One indistinct direction ZINKENITE
Pb₉Sb₂₂S₄₂ Hexagonal Usually massive, also in columnar and radiating fibrous aggregates of needle-like crystals 5.2 to 5.3 Rare

3 to 3½ Tin-white Silvery-grey, shiny One perfect, one distinct, and one imperfect direction ANTIMONY
Sb Trigonal Usually massive, foliated, or granular, rarely as pseudo-cubic or thick tabular crystals 6.6 to 6.7 Very brittle. Rare

Hardness Color Streak Cleavage Name System Habit SG Notes

3 to 4½ Steel-grey, may tarnish dead black upon exposure Black (may be Brownish-black) TETRAHEDRITE/
TENNANTITE
(Cu,Fe)₁₂Sb₄S₁₃(Cu,Fe)₁₂As₄S₁₃ Isometric Usually massive or granular, crystals uncommon and usually pseudo-tetrahedral 4.6 to 5.1 End members difficult to distinguish without subtle tests – an S.G. above 4.7 is conclusive for tetrahedrite.

3½ Tin-white, tarnishing to Dark-grey Grey-black One perfect (basal) ARSENIC
As Trigonal Usually found in botryoidal fibrous masses 5.7 Heated in candle flame it gives off white fumes that have a strong garlic odor (poisonous!) Rare

3½ to 4 Brownish-bronze to Bronze-yellow Black No cleavage but large grains exhibit an octahedral parting PENTLANDITE
(Fe,Ni)₉S₈ Isometric Usually massive in granular aggregates 4.6 to 5.0 Resembles pyrrhotite but is not magnetic, often mixed with pyrrhotite

3½ to 4 Brass-yellow, often iridescent Black CHALCOPYRITE
CuFeS₂ Tetragonal Usually massive, crystals blocky tetrahedrons or wedge-shaped. 4.1 to 4.3 Often mixed with pyrite, making a hardness test inconclusive; distinguished from pyrite by softness and shape of crystals.

3½ to 4 Brown to Black Brown Good in one direction, poor in another direction WURTZITE
ZnS Hexagonal Usually massive and as banded botryoidal crusts, more rarely as pyramidal hemimorphic crystals 4.0 to 4.1 Rare

Hardness Color Streak Cleavage Name System Habit SG Notes

3½ to 4 Dark-brown to black, sometimes Olive-yellow or Red ("Ruby Jack") to Reddish-black Dark to Light-brown: streak usually lighter than the color of the sample Perfect in six directions, three directions usually prominent SPHALERITE
ZnS Isometric Usually in compact crystalline masses, crystals usually blocky pyramidal, appearing tetrahedral 3.9 to 4.1 Luster actually resinous, appearing metallic or submetallic

3½ to 4 Ruby-red to Reddish-brown Brownish-red CUPRITE
Cu₂O Isometric Usually massive, crystals usually cubes or octahedrons 6.0 Luster may be adamantine rather than metallic in crystals

3½ to 4 Black Green One perfect direction ALABANDITE
MnS Isometric Usually massive or granular. 4.0 to 4.1 Rare

Hardness Color Streak Cleavage Name System Habit SG Notes

4 Brownish-bronze to Bronze-yellow Grey-black PYRRHOTITE
Fe_1-xS Monoclinic
pseudo-
hexagonal Usually massive, crystals as pseudo-hexagonal plates 4.6 to 4.7 Magnetic, though may be weak

4 Steel-grey to Iron-black Black Indistinct in two directions STANNITE
Cu₂FeSnS₄ Tetragonal Usually massive, rarely as pseudo-octahedral crystals 4.3 to 4.5 Rare

4 Steel-grey to Iron-black Dark reddish-brown to Black One perfect, two good directions MANGANITE
MnO(OH) Monoclinic, pseudo-
orthorhombic Usually in radiating fibrous masses, crystals often grouped in bundles. 4.3 Often associated with pyrolusite; distinguished from that species by its significantly greater hardness

4 to 4½ White to Steel-grey Grey, shiny PLATINUM
Pt Isometric Usually massive in irregular grains or nuggets, crystals rare and usually malformed cubes 14 to 19 Malleable, very heavy! Very rare. Distinguished from gold by its color.

Hardness Color Streak Cleavage Name System Habit SG Notes

5 Steel-grey Black One perfect direction GLAUCODOT
(Co,Fe)AsS Orthorhombic Usually massive, more rarely as prismatic crystals in cruciform penetration twins 5.9 to 6.1 Rare; alloclasite, monoclinic, is dimorphous with glaucodot and difficult to distinguish from it, but is probably even rarer

5 Yellowish or reddish-brown Pale-brown to white Variable: may be good in one direction and poor to good in another direction MONAZITE
(Ce,La,Nd)PO₄ Monoclinic Usually massive, granular, may be in crude large crystals 4.6 to 5.3 (approx.) Luster usually resinous to waxy, but may be adamantine and may appear sub-metallic

5 to 5½ Dark-brown to Black: color black in ferberite brown in hübnerite Dark-brown to Black: streak darkens with increasing Fe content 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 about 7.3 indicates ferberite, lower indicates hübnerite

5 to 5½ Pale Copper-red to Pinkish silvery-white, tarnishing to Dark-grey or Black Black NICKELINE
NiAs Hexagonal Usually massive, crystals rare and usually pyramidal, often malformed, may also be reticulated or arborescent 7.78 May be coated with green "nickel bloom" (annabergite).

5 to 5½ Dark brown to Black Yellow-brown or Yellow-ocher One perfect direction GOETHITE
(pronounced "Ger-ta-ite.")
FeO(OH) Orthorhombic Usually in radiating botryoidal aggregates, mammillary, or stalactic 4.37

Hardness Color Streak Cleavage Name System Habit SG Notes

5½ Dark-brown to Black Iron-black to Brownish-black CHROMITE
FeCr₂O₄
(Magnesiochromite is closely related, S.G. 4.2, Rare.
Manganochromite, H. 6½, is even rarer.)
Isometric Usually massive, rarely as octahedral crystals 4.6 Luster usually pitchy, submetallic, usually associated with peridotite rocks and accompanied by green or yellow alteration products.

5½ to 6½ Dark-brown to Steel-grey to Black Rust-red or Indian-red HEMATITE
Fe₂O₃ Trigonal Usually massive in radiating, reniform, or micaceous aggregates 4.8 to 5.3 Usually harder than a knife, but some forms can be softer. (See under Tables IA & IC.)

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Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
1 to 2	Iron-black	Black	One perfect direction	PYROLUSITE MnO₂	Tetragonal	May be splintery or in radiating fibrous masses	4.7	Will sometimes mark paper.
1½ to 2	Silvery-white	Grey		SYLVANITE (Au,Ag)Te₂	Monoclinic	Usually granular or in bladed aggregates, often appears as skeletal forms on rocks, resembling writing (cuneiform)	8 to 8.2	May mark paper. Rare
1½ to 2	Metallic-blue, tarnishes to blue-black	Black	One perfect direction (basal)	COVELLITE CuS	Trigonal	Platy masses or thin six-sided platy crystals	4.6	May be somewhat iridescent, turns metallic-purple when wet. Will sometimes mark paper.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
2	Bluish-black to Silvery-black	Grey-black	One perfect direction (prismatic), two imperfect	STIBNITE Sb₂S₃	Orthorhombic	Usually as thick bladed crystals with striations both parallel to and across the long axis; crystals often bent or "kinked"	4.5	Fuses in a candle flame. Will sometimes mark paper.
2 to 2½	Deep Ruby-red to Bright Ruby-red	Brownish-red to Scarlet or Vermilion	One distinct direction	PYRARGYRITE/ PROUSTITE Ag₃(Sb,As)S₃Ag₃(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 a candle flame. Rare.
2 to 2½	Grey-black to Lead-grey	Black		ACANTHITE Ag₂S	Isometric	Pseudo-cubic, usually massive	7.3	Bright steel-grey on fresh surfaces but darkens upon exposure, easily cut with a knife (sectile). Will usually mark paper.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
2½	Bluish-black to Lead-grey	Grey-Black to Black	Perfect in three directions at 90^o to each other	GALENA PbS	Isometric	Usually in cubic crystals or masses exhibiting cubic cleavage, also in granular masses	7.6	Will usually mark paper. Most common heavy mineral.
2½	Brass-yellow to Silvery-white	Yellowish to Greenish-grey		CALAVERITE AuTe₂	Monoclinic	Usually granular, rarely in distinct elongated crystals	9.35	Very heavy, easily fusible in a candle flame (leaving globules of gold). May mark paper. Rare.
2 to 3	Grey-black	Black	One good direction	JAMESONITE Pb₄FeSb₆S₁₄	Monoclinic	Dense clusters or carpets of fibrous to acicular crystals; very delicate!	5.5 to 6.0	Fuses easily in a candle flame.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
2½ to 3	Grey-black	Grey to Black		BOURNONITE PbCuSbS₃	Orthorhombic	Usually in stout prismatic crystals often as intergrown clusters with twinning exhibited by re-entrant angles	5.8 to 5.9	Fuses easily in a candle flame
2½ to 3	Steel-grey, may tarnish to black on exposure	Grey to Black		CHALCOCITE Cu₂S	Monoclinic, pseudo- orthorhombic	Usually in compact masses, crystals tabular to stoutly prismatic, often with a pseudo-hexagonal outline, vertically striated.	5.7
2½ to 3	Dark metallic Blue to Black	Black		DIGENITE Cu₉S₅	Isometric	Usually massive as small to tiny irregular grains, very rarely as octahedral crystals	5.5 to 5.7	Very similar to chalcocite, but much rarer in non-microscopic sizes.
2½ to 3	Steel-grey, tarnishes metallic blue	Dark steel-grey		STROMEYERITE AgCuS	Orthorhombic, pseudo- hexagonal	Usually massive, granular, rarely as pseudo-hexagonal prismatic crystals	6.2 to 6.3	Rare.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
2½ to 3	Lead-grey	Brown to brownish-grey	One distinct direction	BOULANGERITE Pb₅Sb₄S₁₁	Monoclinic	Usually massive as fibrous bundles, crystals usually needle-like mats, prismatic crystals rarer	6.0 to 6.3	Thin acicular crystals flexible. Rare.
2½ to 3	Dark-red to Vermilion	Dark-red	One perfect direction	CINNABAR HgS	Trigonal	Usually massive, crystals uncommon and usually rhombohedral, often as penetration twins	8.10	Luster actually adamantine, appearing metallic, heavy.
2½ to 3	Copper-red on fresh surfaces, tarnishes to brown or black	Coppery-red, shiny		COPPER Cu	Isometric	Usually in irregular masses, large grains, wires, and crude dendritic crystals, crystals usually octahedral and malformed, may be cubic or other Isometric forms	8.9	Malleable.
2½ to 3	Golden-yellow, shiny, becoming paler with increased Ag content - electrum variety	Golden-yellow, shiny		GOLD Au	Isometric	Usually massive in irregular grains, nuggets, "leaves" and "flakes", crystals often wires crudely dendritic or as malformed octahedrons	15.0 to 19.3	Malleable, very heavy! Rare. Distinguished from pyrite – "fools gold" – by its malleability, softness and weight.
2½ to 3	Silvery-white, tarnishes black	Silvery-white, shiny		SILVER Ag	Isometric	Usually massive as irregular grains, wires, and dendritic crystals	10.5	Malleable, heavy. Rare. May mark paper.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
3	Grey-black	Black	One perfect (prismatic), two distinct, and one indistinct direction	ENARGITE Cu₃AsS₄	Orthorhombic	Usually in bladed masses	4.4	Crystals vertically striated
3	Brownish-bronze on fresh surfaces, tarnishing to metallic purple, iridescent ("peacock ore")	Grey-black		BORNITE Cu₅FeS₄	Orthorhombic, pseudo- tetrahedral	Crystals usually pseudo-cubic, usually massive	5.1	Thin splinters fusible in a candle flame, giving a brittle magnetic globule.
3 to 3½	Brass-yellow	Black, sometimes with a greenish tinge		MILLERITE NiS	Trigonal	Usually in radiating groups or mats of needle-like to hair-like crystals	5.5	Slender crystals usually have a greenish tinge
3 to 3½	Steel-grey	Steel-grey	One indistinct direction	ZINKENITE Pb₉Sb₂₂S₄₂	Hexagonal	Usually massive, also in columnar and radiating fibrous aggregates of needle-like crystals	5.2 to 5.3	Rare
3 to 3½	Tin-white	Silvery-grey, shiny	One perfect, one distinct, and one imperfect direction	ANTIMONY Sb	Trigonal	Usually massive, foliated, or granular, rarely as pseudo-cubic or thick tabular crystals	6.6 to 6.7	Very brittle. Rare
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
3 to 4½	Steel-grey, may tarnish dead black upon exposure	Black (may be Brownish-black)		TETRAHEDRITE/ TENNANTITE (Cu,Fe)₁₂Sb₄S₁₃(Cu,Fe)₁₂As₄S₁₃	Isometric	Usually massive or granular, crystals uncommon and usually pseudo-tetrahedral	4.6 to 5.1	End members difficult to distinguish without subtle tests – an S.G. above 4.7 is conclusive for tetrahedrite.
3½	Tin-white, tarnishing to Dark-grey	Grey-black	One perfect (basal)	ARSENIC As	Trigonal	Usually found in botryoidal fibrous masses	5.7	Heated in candle flame it gives off white fumes that have a strong garlic odor (poisonous!) Rare
3½ to 4	Brownish-bronze to Bronze-yellow	Black	No cleavage but large grains exhibit an octahedral parting	PENTLANDITE (Fe,Ni)₉S₈	Isometric	Usually massive in granular aggregates	4.6 to 5.0	Resembles pyrrhotite but is not magnetic, often mixed with pyrrhotite
3½ to 4	Brass-yellow, often iridescent	Black		CHALCOPYRITE CuFeS₂	Tetragonal	Usually massive, crystals blocky tetrahedrons or wedge-shaped.	4.1 to 4.3	Often mixed with pyrite, making a hardness test inconclusive; distinguished from pyrite by softness and shape of crystals.
3½ to 4	Brown to Black	Brown	Good in one direction, poor in another direction	WURTZITE ZnS	Hexagonal	Usually massive and as banded botryoidal crusts, more rarely as pyramidal hemimorphic crystals	4.0 to 4.1	Rare
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
3½ to 4	Dark-brown to black, sometimes Olive-yellow or Red ("Ruby Jack") to Reddish-black	Dark to Light-brown: streak usually lighter than the color of the sample	Perfect in six directions, three directions usually prominent	SPHALERITE ZnS	Isometric	Usually in compact crystalline masses, crystals usually blocky pyramidal, appearing tetrahedral	3.9 to 4.1	Luster actually resinous, appearing metallic or submetallic
3½ to 4	Ruby-red to Reddish-brown	Brownish-red		CUPRITE Cu₂O	Isometric	Usually massive, crystals usually cubes or octahedrons	6.0	Luster may be adamantine rather than metallic in crystals
3½ to 4	Black	Green	One perfect direction	ALABANDITE MnS	Isometric	Usually massive or granular.	4.0 to 4.1	Rare
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
4	Brownish-bronze to Bronze-yellow	Grey-black		PYRRHOTITE Fe_1-xS	Monoclinic pseudo- hexagonal	Usually massive, crystals as pseudo-hexagonal plates	4.6 to 4.7	Magnetic, though may be weak
4	Steel-grey to Iron-black	Black	Indistinct in two directions	STANNITE Cu₂FeSnS₄	Tetragonal	Usually massive, rarely as pseudo-octahedral crystals	4.3 to 4.5	Rare
4	Steel-grey to Iron-black	Dark reddish-brown to Black	One perfect, two good directions	MANGANITE MnO(OH)	Monoclinic, pseudo- orthorhombic	Usually in radiating fibrous masses, crystals often grouped in bundles.	4.3	Often associated with pyrolusite; distinguished from that species by its significantly greater hardness
4 to 4½	White to Steel-grey	Grey, shiny		PLATINUM Pt	Isometric	Usually massive in irregular grains or nuggets, crystals rare and usually malformed cubes	14 to 19	Malleable, very heavy! Very rare. Distinguished from gold by its color.
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
5	Steel-grey	Black	One perfect direction	GLAUCODOT (Co,Fe)AsS	Orthorhombic	Usually massive, more rarely as prismatic crystals in cruciform penetration twins	5.9 to 6.1	Rare; alloclasite, monoclinic, is dimorphous with glaucodot and difficult to distinguish from it, but is probably even rarer
5	Yellowish or reddish-brown	Pale-brown to white	Variable: may be good in one direction and poor to good in another direction	MONAZITE (Ce,La,Nd)PO₄	Monoclinic	Usually massive, granular, may be in crude large crystals	4.6 to 5.3 (approx.)	Luster usually resinous to waxy, but may be adamantine and may appear sub-metallic
5 to 5½	Dark-brown to Black: color black in ferberite brown in hübnerite	Dark-brown to Black: streak darkens with increasing Fe content	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 about 7.3 indicates ferberite, lower indicates hübnerite
5 to 5½	Pale Copper-red to Pinkish silvery-white, tarnishing to Dark-grey or Black	Black		NICKELINE NiAs	Hexagonal	Usually massive, crystals rare and usually pyramidal, often malformed, may also be reticulated or arborescent	7.78	May be coated with green "nickel bloom" (annabergite).
5 to 5½	Dark brown to Black	Yellow-brown or Yellow-ocher	One perfect direction	GOETHITE (pronounced "Ger-ta-ite.") FeO(OH)	Orthorhombic	Usually in radiating botryoidal aggregates, mammillary, or stalactic	4.37
Hardness	Color	Streak	Cleavage	Name	System	Habit	SG	Notes
5½	Dark-brown to Black	Iron-black to Brownish-black		CHROMITE FeCr₂O₄ (Magnesiochromite is closely related, S.G. 4.2, Rare. Manganochromite, H. 6½, is even rarer.)	Isometric	Usually massive, rarely as octahedral crystals	4.6	Luster usually pitchy, submetallic, usually associated with peridotite rocks and accompanied by green or yellow alteration products.
5½ to 6½	Dark-brown to Steel-grey to Black	Rust-red or Indian-red		HEMATITE Fe₂O₃	Trigonal	Usually massive in radiating, reniform, or micaceous aggregates	4.8 to 5.3	Usually harder than a knife, but some forms can be softer. (See under Tables IA & IC.)