Dims: 2.1 x 1.6 x 1.6" (2.3 x 4.1 x 4.1 cm)
Wt: 3.9 oz. (109.7 g)
El Rosario, Baja, California, Mexico
This small hand specimen consists of an apparently massive host rock that is made up of countless intergrown Sanbornite crystals. These crystals are so heavily intergrown that it is nearly impossible to detect any crystal form from them. The crystals have flat faces, though, and a flaky, micaceous consistency. They have a white color and a bright, subadamantine luster that also strongly resembles those of the mica group. As a matter of fact, the only visual difference between this material and muscovite is that muscovite usually has a lower luster! The matrix rock in which the Sanbornite is concentrated appears to be made of quartz or a feldspar, but there is actually more Sanbornite than matrix. Also trapped in the matrix are several incomplete formless, and deep red crystals of Gillespite, a barium iron silicate. Maybe our mineralogist, Dave, should buy this "namesake" piece!