An Update on Color in
Gems. Part 2:
Colors Involving Multiple
Atoms and Color Centers
Gemological Institute of America
Santa Monica, California, USA
George R. Rossman
California Institute of Technolgy, Pasadena, CA, USA
This is the second part in a three-part series on the origin of color
in gem materials. This article discusses colors produced by (1)
processes that involve multiple atoms (e.g., blue sapphire, organic
products), and (2) a variety of defect structures that are generally
created by irradiatin (natural or artificial), known collectively as
"color centers" (e.g., green diamond).
Gems and Gemology 24, 3-15.