| O'Neil, Paul (1983) Planet Earth - Gemstones. Time Life Books, Alexandria, VA. Mason, Anita (1976) The World of Rocks and Minerals. Larousse & Co., Inc., New York. Pratt, Joseph Hyde (1906) Corundum and its occurrence and distribution in the United States (a revised and enlarged edition of Bulletin 180). United States Geological Survey Bulletin 269. |
Yogo Gulch, Yogo District, Little Belt Mountains, Judith Basin County, Montana, USA