- Siglo Veinte Mine (Siglo XX Mine; Llallagua Mine; Catavi), Llallagua, Rafael Bustillo Province, Potosi Department, Bolivia
- Miniature, 4.5 x 2.0 x 1.2 cm
Here we have a remarkable, well crystallized, superb venetian blue color, very rare specimen consisting of radiating crystal aggregates of Vauxite. They are truly terminated crystals and not just a blue mass. The piece is actually a thin shell of Vauxite which may have formed on top of some kind of clay (perhaps decomposed Allophane), which dissolved and left this "crust" of superb blue color Vauxite behind. It is very difficult to obtain any specimens of this incredibly beautiful phosphate. This piece is from the type locality for this material which was discovered along the Contacto and San Jose veins in this mine and was first described by Sam Gordon and Mark Bandy.