Drysdallite is a rare molybdenum selenium sulfide mineral with formula Mo(Se, S)2. It is a rare, opaque molybdenum selenium sulfide mineral. It crystallizes in the hexagonal system as small pyramidal crystals or in cleavable masses.

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

General Information

  • Formula: Mo(Se, S)2
  • Colour: Grayish black with a brown tint
  • Specific Gravity: 6.248 (Calculated)
  • Crystal System: Hexagonal
  • Member of: Molybdenite Group


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.

  • Luster: Metallic
  • Transparency: Opaque
  • Streak: Brownish black
  • Hardness: 2 on the Mohs scale
  • Tenacity: Waxy
  • Cleavage:Perfect on {0001}
  • Density: 6.248 g/cm3 (Calculated)


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