Dumortierite

Dumortierite is called the "blue denim stone." It is named for a French paleontologist, Eugène Dumortier, who discovered it in 1881 in the Rhône-Alps region of France.   Its full name is “blue dumortierite quartz” – quartz referring to crystals composed of silica. It is found in numerous countries.  Dumortierite is fairly hard (Mohs scale 7) and will take a nice polish. It is sometimes mistaken for sodalite and lapis lazuli. Because of the perceived similarity, dumortierite is often used as a cost-saving substitute for lapis which costs two to three times as much.