Demantoid is in fact one of the most brilliant gemstones, although so far generally only collectors and gemstone fans have known about it. Actually it is a green garnet , or should we say the star among green garnets? There is a reason for its name, which comes from Dutch and means something like "similar to diamond”. It refers to the striking characteristic of this gemstone: its unique brilliance and luminosity. Some gemstone dealers have claimed that Demantoid shines and glows even in the shade.
Demantoid is a member of the large gemstone family of garnets. But it is more than that: it is the most expensive garnet variety and one of the most valuable stones of all, highly coveted for its rarity and its incredible brilliance. There is a plausible explanation for this phenomenon: Demantoid has a relatively high refraction of light (1.888). Remarkable, however, is also the dispersion, i.e., its ability to reflect the light coming in through the facets and to dissemble this light into all the colours of the rainbow. Demantoid is a champion in this respect, even better than Diamond.
Demantoid’s colour spectrum includes many shades of green and ranges from slightly yellowish green to brownish green with a golden shine. Most valuable is a deep emerald green, which, however, is very rare indeed. It is not only a fine and rare stone, usually it is also quite small so that larger specimen are difficult to come by. Only few stones achieve more than two carats after cutting, most stones weigh about one carat. So should you come across Demantoid set in a piece of jewellery, you will probably be able to expect only smaller stones.
Favourite Stone of Russia’s Star Jeweller
The fascinating world of gemstones knows stories about many beautiful and attractive stone which made a brief comet-like appearance only to disappear again after only a short period. This might almost have happened to Demantoid – hadn’t there been a wandering goatherd in Namibia. But more on this later.
When the Demantoid was first discovered in the Urals mountains in Russia in 1868, it quickly advanced to the position of a much coveted gemstone. Like a comet it it sparkled and shone , displaying its fire at jewellers’ studios in Paris, New York and St Petersburg. Especially Russia’s star jeweller Car Fabergé was fascinated by it because of its striking brilliance, and so he loved to use the stone in his precious objects. But after the difficult times of World War I, the green star lost some of the attention. Only now and then it appeared on the gemstone market, and if that happened at all, it was usually as a stone set into an old piece of jewellery or from leftover storage from the historical occurrences in the Urals. There were single finds of Demantoid also in other places in the world, like e.g. in the Congo or in Korea in 1975, however, the qualities were only suitable for collectors of stones, not for jewellers. The situation changed suddenly when in the middle of the 90s there was discovered a new vein in Namibia which rendered Demantoid in interesting amounts and quality.
The story of how the vein was discovered seems to have been taken from an adventure novel: the setting is Southern Damara-land, near Spitzkoppe mountain, sometimes also termed he African Matterhorn. There is no movement in the vast steppe below the scorching African sun. Far away at the horizon the "black mountains” range seems to be drifting in blue haze. It is a dry and hard land. And yet for an eternity it has been hiding an unknown treasure. Gemstones. Millions of years ago, liquid magma pushed from the very core to the Earth’s surface here, and petrified a little below the actual surface. Wind and weather have in the course of time eroded the layers until only the characteristic granite mountain of the pointed Spitzkoppe remained – and, of course, the precious stones. But nobody had any idea that they existed at all, until in December 1996 a wandering goatherd came across some crystalline structures which struck his interest. After he showed them around in the neighbouring settlement, experts became interested in the matter. Soon tey managed to find out which valuable stones had been discovered. In the meantime, the Namibian government have handed out mining concessions. For these precious stones. Now the rare stones are carefully picked out by hand from the surrounding rocks. As litle as possible of the valuable raw material shall be lost in this process.
Why a horsetail influences the value of Demantoids
Demantoids from Namibia show a vivid light green to a deep bluish-green Their good brilliance is quite striking. Due to the hardness of little below 7 on the Mohs’ scale they are excellently suited for use in jewellery. But they are missing one characteristic which up to then had been characteristic for Demantoid, identifying it without fail at first glance through a microscope: the so-called horsetail-inclusions. Usually radial crystal rays of golden yellow Byssolith appeared in virtually each and every Demantoid – but they are missing in the relatively inclusion-free gemstones from Namibia. Unfortunately this is no good news. After all, these inclusions are not only typical for Demantoid, but may even increase its value if they are very pronounced. This may sound surprising, since inclusions are usually not very coveted since they decrease the transparency of a stone. But horsetail inclusions are quite a different matter in this respect. A beautiful and well-shaped inclusion in Demantoid will considerably increase the value of a stone. Many gemstone collectors are willing to pay extra for such interesting characteristics.
So should you be offered a Demantoid, do not forget to take a look at it through the gemstone microscope. If the stone is of Russian origin, you may see some fibres and strands reminding of a horsetail. In this case you will have reliable proof about the origin of the stone. At the same time, this "fingerprint of nature” proves that you are holding one of the rarest and most valuable gemstones in the world in your hands. However, you are bound to find this rarity also expressed in the price, since Russian Demantoids are valued considerably higher than the equally highly brilliant green garnets from Namibia.