- Cassitierite (twinned)
- Miniature, 5.2 x 4.9 x 3.2 cm
- Viloco Mine, Loayza Province, La Paz Department, Bolivia
- Ex. Kay Robertson
The great tin mines at Viloco have produced some of the most magnificent Cassiterite specimens known. This large miniature is sharply twinned, with superb luster and a deep brown color that is actually gemmy when backlit along a thin edge. It is unusual to find a twin this size from Viloco, and this piece dates back, surely close to when some of the finest Cassiterites were mined there in the early 1900s. Bolivia has probably produced more tin than any other country in the world, and fortunately many great ore crystals survived the process, this among them. For the size, it has exceptional sharpness and condition (only a few minor dings), and it has among the best luster we have seen on one of these old survivors. Contemporary specimens from this mine have a very different look to them. The complex twinning here is unique, so far as I know, to this mine and old finds.