View source for Pleochroism

[[Light]] may be absorbed differently as it passes through a [[crystal]] in different directions. Sometimes the differences are only in degree of [[absorption]] or [[intensity]]. In other cases, however, different [[wavelength]] portions of the transmitted light are absorbed in different directions, resulting in colors. This phenomenon is termed '''pleochroism'''. In the case of [[uniaxial]] materials, there are only two distinct [[optical]] directions and the phenomenon is termed ''[[dichroism]]''. Other materials may be ''[[trichroic]]'', and the pleochroic colors are sometimes very distinct and strong, and are useful in identification. The pleochroic colors reported for various gems are presented in the order X/Y/Z, separated by slashes. 

=Sources=
*Arem, Joel E. ''Color Encyclopedia of Gemstones'', Litton Educational Publishing, Inc.:New York (1977), ''p. xxv''
[[category:Crystallography]]