- Tazna Mine (Tasna Mine; Tazna-Rosario Mine), Cerro Tazna, Atocha-Quechisla District, Nor Chichas Province, Potosi Department, Bolivia
- Toenail, 3.1 x 2.8 x 2.5 cm
Here is a superb twinned crystal of Ferberite. This piece features the classic, "butterfly" twinning of Ferberite along the a (100) face. This piece is a good quality, sharp, lustrous, large, aesthetic jet-black twinned crystal. It has an attractive thick blocky form, and unlike many others, this piece is not cleaved on the top and/or bottom. Twinned crystals from Bolivia have becoming increasingly difficult to obtain in recent years as the price of Tungsten ore has driven the miners to throw all the Ferberite into the crusher, causing thousands of specimens to be lost forever. These twins are definitely the most highly sought after crystal habit from this locality.