Great audiobook "The Chemistry, Properties and Tests of Precious Stones - John MASTIN" online free

This is a good basic introduction to gemstones and their analysis. Admittedly a lot of the scientific tests have been superseded, but the basic properties never change. The first part of the book concentrates on physical properties of most common gems, then outlines the cutting process and ends with several chapters on each of the gemstone families. A useful little book if you are interested in gems. - Summary by Kevin Green