The distinction between precious gems (sapphire, ruby, emerald and diamond) and semi-precious stones (everything else) is no longer used in the professional gemstone trade. Certain gems were once classified as "precious" based on their rarity, value, color and superior gemological characteristics. But these days a number of rare "semi-precious" stones such as alexandrite, demantoid garnet, tsavorite garnet and tanzanite can be just as valuable as ruby, sapphire and emerald.
Some of these gems are not only rare and expensive, but they also have superior gemological characteristics. Tsavorite, the chrome green garnet from East Africa, is a case in point. While not quite as hard as emerald, tsavorite is more durable and is suitable for daily wear rings. Where most emerald has to be treated with oil or resin to fill internal fractures, tsavorite garnet is always untreated. Tsavorite is also notable for its high refractive index, giving it considerably more brilliance than emerald.
Tsavorite is a variety of grossularite garnet that is colored by chromium or vanadium. It is a fairly recent discovery. The first samples were found in 1967 by Campbell Bridges, a Scottish geologist who was doing consulting work for Tiffany & Co. on the original tanzanite deposit in Tanzania. The first tsavorite deposits across the border in Kenya were discovered by Bridges in 1970. The name 'tsavorite' was proposed by Henry Platt, who was president of Tiffany & Co. at the time. The name is derived from Tsavo National Park at the border of Tanzania and Kenya, near Mount Kilamanjaro.
Large tsavorite gems are extremely rare; much rarer than large emeralds. Miners estimate that 85% of the mined material yields gems weighing under 1 carat, while only 10% yields stones over one carat and a mere 2.5% yields stones weighing over two carats. While it is one of our favorite gems, we rarely find clean specimens in the top chrome-green color at a reasonable price.
We're glad to report that we have just found an excellent lot of tsavorite from Tanzania, with more than 40 quality stones over 1 carat. All of these exhibit the intense chrome green that is the hallmark of fine tsavorite. You'll find a good selection of ovals and pears, with most stones between and 1 and 1.25 carats. Most pieces are eye clean, with a few loupe clean stones as well. This is the best lot of tsavorite garnet we've found in many months and prices are very reasonable given the quality and rarity of these gems.
Very large star sapphires with distinct stars are becoming increasingly difficult to find. This 62.28 carat, deep blue star sapphire from Thailand displays a clear star in any type of lighting. Measuring 22.81 by 18.15 mm, this star sapphire is an impressive stone that would make an outstanding pendant.
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Happy gem hunting,Your friends at GemSelect
- First Published: February-01-2011
- Last Updated: October-21-2014
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