Thometzekite

Thometzekite


Composition: PbCu2+2(AsO4)2.2H2O
Crystal System : Triclinic
Colours: Blue, aqua blue, green, white
Lustre : Waxy, earthy
Hardness (H) : 4-5
Year of Discovery: 1980
IMA Number: 1982-103
IMA Status: Approved
Discovered By: John Innes (Tsumeb mineralogist) and Wolfgang Bartelke (German collector)
Named for: Wilhelm Thometzek (Tsumeb mine director)

Tsumeb is the Type Locality.

Distribution

Very rare.  The location from which the type specimen was recovered is not known. 

Occurrence

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

Paragenetic and General Notes

Thometzekite was the third-discovered member of the tsumcorite group (after tsumcorite and helmutwinklerite).

On the type specimen, thometzekite occurs as tabular crystals to 20μm, but only in the order of 1μm in thickness. It is bluish green to green, with an earthy lustre (due largely to the fine grain-size), and associated with massive gypsum and, according to Schmetzer et al., (1985), tabular mimetite.  The latter was subsequently found to contain cadmium in partial substitution for lead, and described as a new mineral, vanackerite (Schlüter et al., 2016).

In another find, thometzekite is associated with anglesite and quartz, while ferroan thometzekite occurs in an unusual paragenesis with anhydrite, chalcanthite, lammerite and leightonite, discovered on 35 Level in the second oxidation zone.

Recent analysis of a pale, spearmint-green partial coating on the type specimen for schultenite, (specimen number BM.1926,025 in the Natural History Museum, London) has demonstrated the presence of thometzekite as part of the schultenite type assemblage (Mike Rumsey, personal communication to M. Southwood, October 2015).  This appears to be the first confirmed observation of thometzekite from the first oxidation zone.  The schultenite type specimen originates from 7 Level.