World Of Gems Conference 2017 Proceedings Book

WORLD OF GEMS CONFERENCE V - 53 - SEPTEMBER 2017 EFFECTS OF CHROMIUM CONCLUSION The same number of oxygen atoms surround the Cr 3+ as emerald, ruby, and alexandrite although those oxygen ions are in a differing pattern, at different distances from the Cr 3+ (Gem-A 2009). The host materials then interact with the chromium differ- ently. When the electrons are excited (illuminated), it causes absorption of certain wavelengths of light, resulting in color (Fritsch and Rossman, 1987). The difference in body color can be directly related to how much energy (i.e., sunlight) is required for an electron to jump from one level to another. u REFERENCES: Douma, M. (2008). Emeralds, alexandrite and self-colored gemstones In Cause of Color. http://www.webexhibits.org/causesofcolor/6AB.html Douma,M.(2008).Why are rubies red? In Cause of Color. http://www.webexhibits.org/causesofcolor/6AA.html Fritsch, E., and Rossman G.R. (1987) "An update on Color in Gems. Part 1: Introduction and Colors Caused by Dis- persed Metal Ions." Gems & Gemology Vol. 23.NO.3 Gemmological Association of Great Britain, (2009) Diploma in Gemmology London section D7 pg 23-24 Sicree, A. A. (2007)"Chrome, Rubies, Emeralds, and Alexandrite." Popular Mineralogy #7 http://worcestermineralclub.org/wp- content/uploads/2015/03/PopMin-07a.pdf https://cbc-wb01x.chemistry.ohio- state.edu/~woodward/ch754/lect2003/optical1_lect21.pdf