Arsentsumebite

Arsentsumebite


Composition: Pb2Cu(AsO4)(SO4)(OH)
Crystal System : Monoclinic
Colours: Grass-green, apple-green, spearmint-green, blue-green
Lustre : Vitreous (crystals). Earthy (massive)
Hardness (H) : 4.0-4.5
Specific Gravity (S.G) : 6.46
Year of Discovery: 1965
IMA Number: 1935(?)
IMA Status: Approved
Discovered By: Karl Biehl
Named for: Composition/relationship
References: Bideaux et al. (1966)

 Tsumeb is the Type Locality

Distribution

Common. Occurs in considerable abundance throughout much of the first oxidation zone. However, the type material for the 1966 description is probably from the second oxidation zone.

Occurrence

  • Supergene
  • 1st Oxidation Zone
  • 2nd Oxidation Zone

Notable Finds

As spectacular pseudomorphs after mimetite in the upper levels of the mine (many of which were originally considered to be bayldonite after mimetite). In 1989 fine specimens of azurite on arsentsumebite were recovered during pillar-robbing operations on 6 Level (Von Bezing et al., 2014). Many azurites from the famous "Easter Pocket", recovered from 8 Level in 1994, are associated with arsentsumebite.

Paragenetic and General Notes

The arsenate analogue of tsumebite; common in the first oxidation zone. The name arsentsumebite was coined by Vésignié (1935) but, although he chanced on the correct formula, it transpired he had been working with a mixture of bayldonite and duftite (Gebhard, 1999). Despite this, the IMA lists arsentsumebite as "Grandfathered" from 1935. Bideaux et al. (1966) described arsentsumebite as a species in its own right. As crusts of small, platy crystals, typically <1 mm, and often twinned.

Arsentsumebite has been reported to form pseudomorphs after the following minerals:  azurite (rare); cerussite (rare); mimetite (common); schultenite (rare); tennantite (rare).