These are tools and references that I use and recommend. I don't recommend cheap tools often found on eBay.
A spreadsheet program that calculates the Optic Sign, Birefringence and specific Gravity of your stone based on a few simple measurements.
Mac, iPad, iPhone version. Requires Apple Numbers spreadsheet app. The will download as a ZIP file.
Gemstone Software for the Professional Gemologist, student or gemstone enthusiast. Includes Gemstone Database of over 500 gems, gemstone separator, inclusion gallery and much more.
Available from: Gemology Tools Pro
Very handy reference book, good for all levels. Find it on Amazon