Calcite

Creel, in the Sierra Tarahumara region of Chihuahua, is better known for its rugged landscape and copper canyon country than for a major calcite deposit. Clear optical calcite, also called Iceland spar, has been documented from Creel and the surrounding region. This variety is valued for its ability to split light into two images, a property known as double refraction. This specimen comes from the collection of John C. White.