Gem/Gem Topic of the Month

Each month this section will feature either a topic of interest to gem lovers or one special gemstone with background on the material and its value.

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February, 1998 (Revised, August, 2004)

Tsavorite Garnet

Tsavorite, or transparent, green grossular garnet, was discovered in Kenya in the 1960's and given its trade name by Tiffany marketers based on the proximity of Tsavo National Park to the mine sites. It is one of the most sought after and valuable types of garnet.

The geologic deposits in which it is found are difficult and expensive to mine and unpredictable in distribution so production as been sporadic. Political conflicts and trade issues further endanger the reliable supply. The crystals which are found show evidence of being affected by tremendous geologic forces, and as a result are seldom found large and clean. Cut specimens over 3 carats are exceedingly rare.

The color ranges from lime green to emerald green to pure spectral green and is caused by high vanadium content. Rarely found better than eyeclean, typical inclusions are straight or angular corrosion growth tubes, fingerprints, feathers, veils and graphite inclusions. Like all types of garnet this stone is the birthstone for the month of January.

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Given the rarity, popularity, and sporadic supply of these stones, the overall trend in value since their introduction has been up, up, up. The best specimens are those that are pure spectral green in a medium dark to medium tone. Those that are darker or lighter than this are much less desirable. Price exponentially increases with size and a custom cut adds considerable value as the majority of specimens are native cut.

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Gemological Data

Makeup: a calcium aluminum silicate

Luster: Vitreous

Hardness: 7

Fracture: conchcoidal to uneven

Density: 3.61

RI: 1.74