Oldhamite

Oldhamite
Oldhamite (field of view: 1.5 cm)
General
CategorySulfide mineral
Formula
(repeating unit)
(Ca,Mg)S
IMA symbolOld[1]
Strunz classification2.CD.10
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFm3m
Unit cella = 5.69 Å; Z = 4
Identification
ColorPale chestnut-brown
Crystal habitCrystal nodules, anhedral grains
CleavageGood on {001}
Mohs scale hardness4
LusterSub-metallic
DiaphaneityTransparent
Specific gravity2.58
Optical propertiesIsotropic
Refractive indexn = 2.137
Fusibility2450 °C
Alters toTarnishes 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.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Handbook of Mineralogy
  3. ^ a b Oldhamite on Mindat.org
  4. ^ a b Webmineral dat for oldhamite