Chemistry:Drysdallite

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Drysdallite
Drysdallite.jpg
General
CategoryMineral
Formula
(repeating unit)
MoSe1.5S0.5
Strunz classification2/D.25-30
Dana classification1.12.10.2
Crystal systemHexagonal - Dihexagonal Dipyramidal
Space groupP63/mmc (No. 194)
Unit cell120.94 ų (Calculated from Unit Cell)
Identification
Formula mass230.41 gm
ColourGrayish-black
CleavagePerfect
TenacityWaxy, pliable, difficult to pulverise
Mohs scale hardness2
|re|er}}Metallic
StreakBrown-black
Specific gravity6.248 (Calculated)
Density6.248 g/cm3 (Calculated)
PleochroismStrong, white to very pale grey, to pinkish grey

Drysdallite is a rare molybdenum selenium sulfide mineral with formula Mo(Se,S)2. It crystallizes in the hexagonal system as small pyramidal crystals or in cleavable masses. It is an opaque metallic mineral with a Mohs hardness of 1 to 1.5 and a specific gravity of 6.25. Like molybdenite it is pliable with perfect cleavage.

It was first described in 1973 for an occurrence in an oxidized uranium deposit near Solwezi, Zambia. It was named for Alan Roy Drysdall, the director of the Zambian geological survey.

References