Gübelin, Eduard J. & Koivula, John I. (2005) Photoatlas of Inclusions in Gemstones, Volume 2. Opinio Publishers, Basel, Switzerland, 830 pp. ISBN 978-3855040957
A brief look at the famous emerald and alexandrite from Russia's Ural Mountain mines.
The history of Thailand's famous relic.
One of the greatest gemological challenges is determining if a ruby or sapphire has been heat treated. UV fluorescence can assist in that identification, as well as detecting fillers in emerald.