Sillimanite

Sillimanite is a silicate with composition Al₂SiO₅ . This sample is about 0.5x0.8 cm and is from Burma. The chemical compostion is the same as the mineral andalusite and kyanite. These samples are on display at the Smithsonian Museum of Natural History.

The gem is 24.9 carats and the small sample is about .4x1 cm. They are from Sri Lanka.