Oldhamite | |
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General | |
Category | Sulfide mineral |
Formula (repeating unit) | (Ca,Mg)S |
IMA symbol | Old[1] |
Strunz classification | 2.CD.10 |
Crystal system | Cubic |
Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
Space group | Fm3m |
Unit cell | a = 5.69 Å; Z = 4 |
Identification | |
Color | Pale chestnut-brown |
Crystal habit | Crystal nodules, anhedral grains |
Cleavage | Good on {001} |
Mohs scale hardness | 4 |
Luster | Sub-metallic |
Diaphaneity | Transparent |
Specific gravity | 2.58 |
Optical properties | Isotropic |
Refractive index | n = 2.137 |
Fusibility | 2450 °C |
Alters to | Tarnishes on exposure to moist air |
References | [2][3][4] |
Oldhamite is a calcium magnesium sulfide mineral with the chemical formula (Ca,Mg)S.[2][3] Ferrous iron may also be present in the mineral resulting in the chemical formula (Ca,Mg,Fe)S.[4] It is a pale to dark brown accessory mineral in meteorites. It crystallizes in the cubic crystal system, but typically occurs as anhedral grains between other minerals.