Physical Properties of Ore Minerals

Table 2. Hexagonal Crystal Class - Hexagonal Subystem

© Charles E. Corry

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

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Mineral NameCompositionSpace GroupResistivity (ohm-m)Dielectric PermittivityCharge Separation PhenomenaCurie Temp. °CMagnetic Properties k×10-6cgsOptical PropertiesR %Comments
Zinkenite (keeleyite)Pb6Sb14S27PbSb2S4C66  pyroelectric  weak to distinct pleochroism, distinct anisotropy, weak bireflectance.Ro-33.7
Also falls in space group C6h2.
BerndtiteSnS2C6v4  pyroelectric<680 weak bireflectance, slight anisotropy.~25Also given as trigonal, space group C3v1.
GreenockiteCdSC6v4semiconductor9pyroelectric diamagnetic
k = -50
moderate birefringence19.4Forms solid solution with wurtzite and hawleyite.
WurtziteZnSC6v4semiconductor 3.5×1028pyroelectric diamagnetic
k = -25
moderate birefringence16.5Dimorphic with sphalerite and matraite.
ZinciteZnOC6v4semiconductor12pyroelectric  anisotropy masked by internal reflections, moderate birefringence.11.8 
TroiliteFeSD3h4p-type metal
10-6 to 10-1
>81ferroelectric van den Berg et al. (1969)127antiferromagnetic
k = 5,187
Tn = 320-340°C
very distinct pleochroism, very strong anisotropy, very distinct bireflectance.37.5End member of solid solution with pyrrhotite. Uniaxial ferroelectric.
AchavaliteFeSeD6h4  ferroelectric ? (isostructural)  no data  
Blaubleibender covelliteCu1+xSD6h4metal
10-7 to 10-3
 ferroelectric ? (isostructural)<157 remains blue, strong anisotropy.Ro-8.2
CovelliteCuSD6h4p-type metal
10-7 to 10-3
 ferroelectric ? (isostructural)<500diamagnetic
k = -2
extreme pleochroism, extremely anisotropic, very strong bireflectanceRo-6.4
Forms solid solution with chalcocite and hawleyite.
FrebolditeCoSeD6h4   ferroelectric ? (isostructural)  strong anisotropy, very weak bireflectance.~48 
10-8 to 103
>81ferroelectric ? (isostructural) diamagnetic
k = -13
extreme pleochroism, extremely anisotropic, extreme bireflectance.Ro-17.4
Dimorphic with diamond and chaoite. No elements are presently known to form ferroelectric crystals.
IdaiteCu5FeS6D6h4  ferroelectric ? (isostructural)  very high pleochroism, enormous anisotropy, very strong bireflectance.26.9 to 29.8 
ImgreiteNiTeD6h4  ferroelectric ? (isostructural)  no data  
JaipuriteCoSD6h4  ferroelectric ? (isostructural)  no data  
KlockmanniteCuSeD6h4  ferroelectric ? (isostructural) diamagnetic
k = -20
extreme pleochroism, extreme anisotropy, very strong bireflectance.15.6 to 37.2 
KotulskitePdTeD6h4  ferroelectric ? (isostructural)  distinct bireflectance, strongly anisotropic.63.7Forms solid solution with merenskyite and moncheite.
Millerite (high)NiSD6h4semiconductor
4×10-7 to 2
 ferroelectric ? (isostructural)<379antiferromagnetic
k = 1045
Tn = -10°C
distinct pleochroism, strongly anisotropic, distinct bireflectance in oil.Ro-49.4
mixed type
>81ferroelectric ? (isostructural)<1675diamagnetic
k = -63 to -77
extreme bireflectance, very high pleochroism, very strong anisotropy.Ro-38.6
Measurable surface charge on crystal faces at 25C. May also be trigonal, space group C3v5.
10-7 to 10-5
 ferroelectric ? (isostructural)  high pleochroism, very strong anisotropy, strong bireflectance.47.2 to 51.6 
NigglitePtTe + PtSn ?D6h4  ferroelectric ? (isostructural)  very high bireflectance, extreme anisotropy45.4 to 57.8 
PyrrhotiteFe1-xS (x<0.04) Fe7S8 (x>0.04)D6h4p-type metal
10-6 to 10-1
>81ferroelectricvan den Berg et al. (1969), van den Berg (1970, 1972)>100 for x<0.04Fe7S8 is ferrimagnetic at room temperature
Tc=300 to 325°C
k=102 to 5×105
mean 1.25×105
very distinct pleochroism, very strong anisotropy, very distinct bireflectance.Ro-34.0
Forms solid solution with albandite, jaipurite, millerite, niningerite, and pyrite. Troilite is antiferromagnetic with k = 5,187, Tn=320 to 340°C
TungsteniteWS2D6h4  ferroelectric ? (isostructural) 
k = 5,850
extreme bireflectance, very high pleochroism, very strong anisotropy.18.1 to 35.7Optically difficult to distinguish from molybdenite.
Water Hexagonal iceCubic iceH2OD6h4mean 4.7×105>80ferroelectric Dengel et al. (1964), Cubotti and Geracitano (1967) -80 to 173  OT 

Ore Minerals - 29 JAN 1997

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