Aktashite is a rare arsenic sulfosalt mineral with formula Cu6Hg6As4S12. It is a copper mercury-bearing sulfosalt and is the only sulfosalt mineral with essential Cu and Hg yet known. It is of hydrothermal origin. It was published without the approval of the IMA-CNMNC, but recognize as valid species by the IMA-CNMNC Sulfosalts Subcommittee (2008).

General Information

  • Category: Sulfosalt
  • Formula: Cu6Hg6As4S12
  • Crystal system: Trigonal
  • Formula mass: 1667.51 g/mol

The composition and structure of aktashite from the Aktash deposit, Gorny Altai, Russia, have been studied by electron microprobe and X-ray structural analysis. On the basis of close compositions and crystal structures, the identity of aktashite from the Gal-Khaya and Aktash deposits has been demonstrated.

Physical Properties of Aktashite

  • Lustre: Metallic
  • Transparency: Opaque
  • Color: Gray-black
  • Comment: white in reflected light
  • Streak: black
  • Hardness: 3½ on Mohs scale
  • Hardness: VHN50 = 300 – 346 kg/mm2 – Vickers
  • Tenacity: Brittle
  • Cleavage: None Observed
  • Fracture: Irregular/Uneven, Conchoidal
  • Density: 5.5 g/cm3 (Measured) and 5.72 g/cm3 (Calculated).

The structure of aktashite as a framework of vertex-shared HgS4 − and CuS4− tetrahedrons of the same orientation is intimately related to the sphalerite-type structure. The earlier identified uncommon cluster group [As4] has been verified and its parameters have been refined. It is shown that the structure may be represented as construction blocks (As4S12)12− packed according to the law of the distorted cubic I-cell.


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