Green Garnets Tsavorite and Demantoid what’s the difference?
They're both Green? They're both Garnets - but the are different !!!
The key difference to the buyer is that the Tsavorite has a very rich bright green and the demantoid usually has a slight yellow hue to the otherwise Bright Green
Example Tsavorite - note the bright rich green
Example Demantoid - note the slight yellow hue & darker toned green compared with the Tsavorite. Note too, this stone is perfectly clear - there is no Horsetail Inclusion (refer below for a discussion) so we can be 95% certain it is from Namibia & not from Russia
Both appear green in colour but chemically they are different (although closely related and both are technically Garnets of a type)
Both stones are more than 1000 times rare than diamond although Demantoid has commanded the higher prices in the past due to its fame in the Russian court back in the days of Imperial Russia
The Molecular model of Garnets have the general formula A3B2(SiO4)3
A is usually one of: Ca, Mg or Fe
B is usually one of: Al, Fe or Cr
Tsavorite has A, B values of: Ca, Al
Demantoid has A,B values of: Ca, Fe
Demantoid is the most expensive kind of garnet and one of the most precious of all gemstones due to a combination of its rarity incredible luminosity. The high luminosity can easily be explained by the fact that the Demantoid has an extremely high refraction. It can split the light which comes in through the facets and break it down into all the colours of the rainbow and does this even better than diamonds can.
Its colour varies from a slightly yellowish green to a brownish green with a golden glow. Particularly expensive is a deep emerald green although this colour is much sought after and is extremely rare indeed. Large stones are almost unknown with nearly all cut stones being less than one Carat.
Why does the horsetail inclusion influence the value of a demantoid ?
Demantoids from Namibia come in shades from a vivacious light green to an intense blue-green and have a striking brilliance. One key difference is that t hey do lack one the microscopic 'horsetail inclusion'. In Russian Demantoid brown crystal threads of chrysotile appear to radiate out from the centre of the stone. The stones from the much more Namibian fields are very clean and do not exhibit this feature. These horsetail inclusions were not only typical of the demantoid they could even increase its value if they were pronounced. That may sound surprising since inclusions are not a welcome sight in most stones but with the Demantoid, the 'horsetail inclusions' is a different matter. A well-formed inclusion can increase the value of the gemstone considerably and many collectors are prepared to pay a much higher price for stones exhibiting this feature.
Exampe Horsetail Inclusion - If a stone has this type of inclusions we can be 95% sure it is from Russia. If it is totally clean then it is most likely sourced frm Namibia. Be careful of this when buying on eBay - just today I could find examples of Demantoid being advetised as 'Russian' but the clarity of the stone being given as VVS or IF - not likely !!! If the Stone is Russian & has a Horsetail inclusion it's going to be more likely an I1 quality stone (more or less) - it's definitely NOT going to be IF or VVS or even VS for that matter.
In approximately 2003 reports began to circulate in the trade that some Russian Demantoid garnets were being routinely subjected to heat treatment in order to enhance their colour. Such treatment is believed to be performed at relatively low temperatures and is not thought to be detectable by gemmological testing.
Tsavorite is a variety of the Garnet group and minute amounts of vanadium or chromium provide the green colour.
It had been extremely rare until 1967 when a British gem prospector and geologist Campbell R. Bridges discovered a deposit of the mineral in the mountains of northeast Tanzania. The specimens found were very intense in colour and of high transparency.
Believing that the deposit was a part of a larger geological structure extending possibly into Kenya, Bridges began prospecting in that nation. He was successful a second time in 1971 when he found the mineral there and was granted a permit to mine the deposit. Until 1974, the gemstone was only known to mineral specialists but Tiffany and Co launched a marketing campaign which brought broader recognition of the stone. The name Tsavorite was proposed by Tiffany and Co president Henry Platt in honour of Tsavo National Park in Kenya. Apart from the source locality in Tanzania it is also found in Toliara (Tuléar) Province, Madagascar, but so far, no other occurrences of gem material have been discovered.
The Tsavorite is a ‘sleeping giant’ of an investment which is bound to increase in value over time due to its scarcity.
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