otavite

Schneider (1906) described tiny curved rhombic crystals (0.4-0.5 mm) in cavities in a white to reddish crust. Qualitative wet chemistry and blowpipe analysis confirmed the presence of cadmium, and a subsequent quantitative wet chemical analysis indicated a pure cadmium carbonate that had not previously been observed in nature. Otavite was the name proposed by Schneider (1906) after "… the Otavi mining field". Otavite has grandfathered status with the IMA, dated 1906 (http://cnmnc.units.it/; accessed January 2023).

Otavite was the first new mineral described from Tsumeb (Schneider 1906), and yet it remains one of the rarest and most elusive from the collector's point of view. Analysis – at least semi-quantitative – is required for reliable identification and many putative otavite specimens turn out to be calcite, dolomite, smithsonite or, at best, Cd-bearing calcite or Cd-bearing smithsonite.

Otavite occurs typically as white, greyish, or yellowish coatings, with minute, rounded rhombohedral crystals, typically < 0.5 mm, with a pearly lustre, usually on smithsonite or on cerussite and commonly (though by no means always) with rosasite. This paragenesis appears to have been limited to the uppermost part of the first oxidation zone.

An outstanding example of otavite extensively encrusting a specimen of cyclically twinned cerussite is in the Feinglos Collection and is now at Harvard University (catalogue number MGMH 2022.4.10042D).

A second paragenesis was described by Joy Désor in 2020, in which minute irregular grains of white otavite were observed superimposed on an unidentified phase and associated with the secondary cadmium sulphates edwardsite and niedermayrite (Joy Désor pers. comm. to M. Southwood, 2020; Joy Désor - New minerals for the Tsumeb mine, Namibia (mindat.org); accessed October 2022).

A third paragenesis reported by Désor comprises mixed crystals with zones of otavite and minrecordite compositions, associated with cerussite (Joy Désor, pers. comm. to M. Southwood, February 2023). This discovery is of additional interest because the occurrence of otavite has hitherto appeared restricted to the upper part of the first oxidation zone, while minrecordite has only been reported from the second oxidation zone. Unfortunately, the location from which Désor’s specimen was recovered is not known.

azurite; calcite; cerussite; edwardsite; gunningite; ktenasite; lauraniite; lazaridisite; malachite; minrecordite; niedermayrite; rosasite; smithsonite