Vesuvianite or Idocrase is a rare gemstone, usually found in shades of green but sometimes in yellow-brown or pale-blue. Idocrase belongs to the silicate group of minerals. Idocrase is not only an uncommon material, but transparent specimens that can be faceted are extremely rare. Most gem-quality idocrase is opaque with an appearance similar to jade. The opaque specimens have a greasy or resinous luster, while the rare transparent form has a vitreous luster.