ncat JP3742 Willemite, Calcite, Mottramite, Cuprite, Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia

This micro specimen came from the Jo Price Collection. Jo had acquired it from the late Jack Nelson. It is an old specimen simply labelled as mimetite, Tsumeb, SWA. The yellow-zoned “mimetite” crystals look odd and have interesting zoning and appear to be almost aggregates, with lots of crystal faces along their length.

Paul De Bondt suggested that this is in fact not mimetite, but cadmium bearing willemite, and to look at the terminations of the crystals where there should be a triangle at the top. Triangles were not particularly evident on my specimen, but I did find a couple of Mindat photos that supported Paul’s identification. In particular, this one from Brent Thorne.

So the new label now reads Willemite (cadmium-bearing), Calcite, Mottramite(?) and Cuprite.

The calcite occurs as simple rhombs, and more complex crystals (or are the latter cerussite?). Cuprite is present as simple cubes (eg: top right of photo) and underlies calcite. And there are small yellow-green crystals of mottramite(?).

Width of view 6mm. Stack of 75 images.

Click on the image below for a higher resolution version.