Table of Refraction in Gems

The table below gives the necessary information as to which stones show double and which single refraction.

TABLE GIVING CHARACTER OF REFRACTION IN THE PRINCIPAL GEMS

Refraction Single:

Diamond

Garnet (all types)

Spinel

Opal

Glass

Refraction Double Difference between highest and

lowest refractive indices

Sphene............................... .084

Zircon............................... .053

Benitoite............................ .047

Peridot or chrysolite................ .038

Epidote.............................. .031

Tourmaline........................... .020

Kunzite.............................. .015

Ruby and sapphire.................... .009

Topaz (precious)..................... .009

Amethyst and quartz topaz............ .009

Emerald and aquamarine............... .007