Physical Properties of Ore Minerals

Table 3. Hexagonal Crystal Class - Trigonal Subystem

Minerals are arranged alphabetically by space group (Schoenflies symbol).

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Mineral Name	Composition	Space Group	Resistivity (ohm-m)	Dielectric Permittivity	Charge Separation Phenomena	Curie Temp. °C	Magnetic Properties k×10-6cgs	Optical Properties	R %	Comments
Stillwaterite	Pd8As3	C31	metal?		pyroelectric				53.1 to 53.7	Also shown as space group C3i1.
Carlinite	Tl2S	C34	semiconductor		pyroelectric		diamagnetic k = -89		39.2 to 40.6 ?
Illmenite	FeTiO3	C32	semiconductor 10-3 to 102	33<e<81	ferroelectric ??	<25	antiferromagnetic k=2.5×104-3×105 mean 1.5×105 Tn=-205 to 216°C	distinct pleochroism, strong anisotropy, rare internal reflections, distinct bireflectance.	Ro-20.1 Re-17.0	Exhibits parasitic ferromagnetism in solid solution with hematite.
Cinnabar	HgS	D34	semiconductor 109 to 1011	18	piezoelectric ferroelectric ??	<344	diamagnetic k = -55	distinct pleochroism in oil, strong anisotropy, common internal reflections often masked by bireflectance.	Ro-24.1 Re-29.6	Dimorphic with metacinnabar and transforms to metacinnabar at 344°C.
Heazlewoodite (chizlewudite)	Ni3S2	D37	metal		piezoelectric	<556	paramagnetic k = 1,030	very weak pleochroism, strong anisotropy.	51.6 to 57.1	Converts to cubic, space group Td2at 556°C.
Alunite	KAl3(OH)6(SO4)2	C3v5			pyroelectric ferroelectric ??			moderate birefringence.	OT	Forms solid solution with jarosite.
Jarosite	KFe3(OH)6(SO4)2	C3v5			pyroelectric ferroelectric ??			extreme birefringence	OT	Forms solid with alunite.
Mäkinenite	NiSe	C3v5			pyroelectric ferroelectric ??			strong bireflectance, extreme anisotropy with peculiar colors.	47.8 to 50.0
Matraite	ZnS	C3v5			pyroelectric ferroelectric ??		diamagnetic k = -25		17.1 to 19.5?	Dimorphic with sphalerite and wurtzite.
Millerite	NiS	C3v5	metal 3×10-7 to 2		pyroelectric ferroelectric ??	<379	Pauli paramagnetic k = 190 to 1045	weak pleochroism in air, moderate in oil, very strong anisotropy, distinct bireflectance in oil.	Ro-49.4 Re-56.6
Molybdenite	MoS2	C3v5	semiconductor mixed type 10-3 to 106	>81	pyroelectric ferroelectric ?	<1675	diamagnetic k = -63 to -77	extreme bireflectance, very high pleochroism, very strong anisotropy.	Ro-38.6 Re-19.5	May also be hexagonal, space group D6h4.
Tourmaline	(Na,Ca)(Li,Mg,Al)· (Al,Fe,Mn)6	C3v5		5.45<e<6.76	pyroelectric			moderate to strong birefringence in Fe variety.	OT	Solid solution with schoridravite and elbaite.
Valleriite	3(Mg,Al)(OH2)· 2FeCuS2	C3v5	semiconductor		pyroelectric ferroelectric ?	<650		enormous bireflectance, extremely anisotropic.	14.2 to 20.2	Vaughn and Craig (1978) give space groups D3d3, D3d5, and C3v5. All are point group 3m except C3v5. Forms solid solution with mackinawite.
Proustite	Ag3AsS3	C3v6	semiconductor 102 to 104	16.5	pyroelectric ferroelectric ??	<300		strong pleochroism, strong anisotropy, abundant internal reflections always commonly doubled, distinct to strong bireflectance, extreme birefringence.	Ro-25.3 Re-27.7	Forms solid solution with pyragyrite.
Pyragyrite	Ag3SbS3	C3v6	semiconductor 102 to 104	222	pyroelectric ferroelectric ??	<300		distinct to strong pleochroism, strong anisotropy, numerous internal reflections, commonly doubled, distinct to strong bireflectance, extreme birefringence.	Ro-28.0 Re-31.0	Forms solid solution with proustite.
Heterogenite (stainierite)	Co2O3·H2O	D3d5			ferroelectric ??			very strong pleochroism, very high anisotropy, very strong bireflectance.	16.4 to 26.3
Siderite (chalybite)	FeCO3	D3d6	semiconductor 10-1 to 1010	5<e<9	ferroelectric ??		antiferromagnetic k = 100 to 310 Tn = -233°C	extreme birefringence, very high bireflectance in reflected light, strongly anisotropic.	OT

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