- Miniature, 3.4 x 2.3 x 0.7 cm
- Siglo Veinte Mine (Siglo XX Mine; Llallagua Mine; Catavi), Llallagua, Rafael Bustillo Province, Potosi Department, Bolivia
Cronstedtite is a rare iron silicate of the serpentine group. This very rich and beautiful specimen is festooned with lustrous, black, trigonal crystals to 1-2 mm on a thin crust of matrix. The crystals are formed into crude botryoids. It is a rare occurrence to have such a rich coverage of cronstedtite, and this specimen displays very well. This is a classic rarity from the famous Siglo XX Mine of Bolivia and is very seldom available.