Rare Purple Garnets from Mozambique

Purple Garnet, Mozambique

The most exciting gem at this year's Tucson gem show was a rare Purple Garnet from East Africa. There were specimens from deposits in Tanzania and Mozambique, with the finest material coming from the Mozambique mine. Indeed, the top grade pieces were among the most beautiful garnets we've seen anywhere. We were lucky to be one of the few dealers able to acquire some of the finest of these unusual gems.

What's special about these garnets is the wonderful color -- an intense purple with red flashes that we call Royal Purple. The Mozambique material in particular has a bright open color with wonderful brilliance. If this wasn't enough, these garnets also display a fascinating color change, from grape under daylight to cranberry with magenta flashes under incandescent lighting.

Purple Garnet Color Change
Purple Garnet Color Change

The GIA lab in Bangkok did some analysis of the Mozambique purple garnets and published their findings in the Fall 2016 edition of Gems & Gemology. The material they tested came from a mine in central Mozambique in Manica province close to the Zimbabwe border. 

Spectrometry showed that the material was a pyrope-almandine garnet with the following chemical components: 48.8-59.5% pyrope, 37.9-47.6% almandine, 2.0-3.5% grossular, and 0.5-0.6% spessartine. Though the chemical composition classifies these gems as rhodolite garnet, analysis of the absorption spectra showed some unique properties. Since the main absorption bands dominate the green-yellow regions of the visible spectrum, two strong blue and red transmission regions combine to produce an eye-visible purple color, and also account for the strong color change.

Under cool light these gems display a rich grape hue. But under incandescent light, which has more wavelengths in the red part of the spectrum, these gems display a blazing cranberry color with magenta flashes. Under balanced lighting, they are an intense purple with red flashes.

The material with the best color is found in smaller sizes, under 3-4 carats. Since the color saturation is so intense, larger stones tend to be too dark. Though the highest grade material has come from the Mozambique deposit, both the Tanzanian and Mozambican material display the distinctive color change.

Royal Purple Garnet

Unfortunately the Mozambique deposit is in a politically unstable area of the country under the control of the Mozambican National Resistance, an armed rebel group. The government has now closed the area to mining and we don't know if and when we will find this material again. So the usual maxim of the gem trade applies -- buy it while you can!

See our collection of fine Purple Garnet from East Africa