Drysdallite

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.

Drysdallite
General
Category	Minerals
Formula	MoSe1.5S0.5
IMA symbol	Dry[1]
Strunz classification	2/D.25-30
Dana classification	1.12.10.2
Crystal system	Hexagonal - Dihexagonal Dipyramidal
Space group	P63/mmc (No. 194)
Unit cell	120.94 ų (Calculated from Unit Cell)
Identification
Formula mass	230.41 gm
Colour	Grayish-black
Cleavage	Perfect
Tenacity	Waxy, pliable, difficult to pulverise
Mohs scale hardness	2
Luster	Metallic
Streak	Brown-black
Specific gravity	6.248 (Calculated)
Density	6.248 g/cm3 (Calculated)
Pleochroism	Strong, white to very pale grey, to pinkish grey

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.