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).
- 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.