Peridot, one of the more attractive green gemstones, is found in a number of mafic & ultramafic volcanic rocks around the world. In Wyoming, peridot was discovered by Professor Hausel in 1997 at Black Rock in the Leucite Hills volcanic field. At the time he was searching for evidence of diamonds when he came across two green-colored anthills that were completely covered with 13,000 carats of facetable peridot!