GEMS Bauer, Max Precious stones, Vol 1 & 2, Dover, 1904, 1968
GEMS Arem, Joel Gems and jewelry. Grosset & Dunlap, 1975
GEMS Arem, Joel E. Color encyclopedia of gemstones. Van Nostrand Reinhold, 1977
GEMS Greenbaum, Walter W. The gemstone identifier. Prentice-Hall, 1988