Chrome Tourmaline from East Africa is a very attractive shade of green which derives it’s unique coloration from the presence of chromium or vanadium.
Tourmaline is a gemstone noted for the large number of colors in which it occurs and since chrome tourmaline is much more rare and valuable than ordinary green tourmaline, chemical analysis has become an increasingly important part of accessing tourmaline value.
In the field, the chrome deposits normally produce similar material so if one stone tests as chrome, we can assume that all the tourmaline from that deposit should also be chrome bearing. The easiest way to determine the presence of chromium or vanadium is by use of the Chelsea or Chrome filter. The dark colored filter will appear red upon inspection of a transparent illuminated chrome or vanadium bearing material.