Gemstone Constants

I created this app for use in the gemmological testing of gemstones. It contains the constant values of commercially known gemstones. The database includes Refractive index (including birefringence, optic sign and character), specific gravity and gemstone spectra.
They are listed Alphabetically, refractive index from low to high and specific gravity from low to high, for easy gemstone identification.

Key Features:
-R.I.'s of commercially known gemstones
-Wikipedia links to commercially known gemstones
-Spectra for relevant gemstones.

Tools required to utilize this app:
-Refractometer
-gemmological scales (for specific gravity)
-Spectroscope