Johnbaumite | |
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General | |
Category | Apatite group |
Formula (repeating unit) | Ca5(AsO4)3OH |
IMA symbol | Jbm[1] |
Strunz classification | 08.BN.05 |
Dana classification | 41.08.03.03 |
Crystal system | Hexagonal |
Crystal class | Dipyramidal (8/m) |
Space group | P63/m |
Identification | |
Colour | Greyish white to colourless |
Crystal habit | Anhedral grains, granular minerals without the expression of crystal shapes and massive, uniformly indistinguishable crystals forming large masses. |
Cleavage | Distinct {1010} |
Fracture | Irregular/Uneven |
Tenacity | Brittle |
Mohs scale hardness | ≈ 4.5 |
Luster | Adamantine to greasy on fracture surfaces, vitreous on cleavage surfaces |
Streak | White |
Diaphaneity | Transparent |
Density | 3.65 – 3.73 g/cm3 |
Optical properties | Uniaxial (−) |
Refractive index | nω = 1.687 nε = 1.684 |
Birefringence | 0.003 |
Pleochroism | Non-pleochroic |
Extinction | Parallel |
References | [2] [3] |
Johnbaumite is a calcium arsenate hydroxide mineral. It was first described in 1980, where it appeared in Franklin Township, Somerset County, New Jersey.[4] Johnbaumite was discovered at Harstigen mine in Sweden in the 19th century, but it was described as svabite.[5]
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