Demantoid Garnet Gemstone Information


Demantoid Garnet

 
Demantoid Garnet is a rare and beautiful bright grass green variety of andradite garnet. It appears to have first been discovered around 1892 in the Bobrovka area of Russia. The Bobrovka is a small tributary of the River Tschussowaja in the Sissersk region on the western side of the Ural Mountains. It was at first thought to be emerald, which is found nearby, and has been erroneously called "Uralian emerald".

The demantoid is one of the most brilliant gemstones that exist, yet until recently it was little known except among collectors and gemstone lovers. Not without reason does it bear a name which means 'diamond-like'. The name comes from the Dutch and makes reference to the outstanding quality of this gem, its incomparable brilliance and fire. Some gemstone lovers claim that a demantoid will continue to glow even in the shade.
 
A diagnostic characteristic of Russian demantoid is the inclusion of radiating fibres of byssolite (asbestos) fibres in a pattern described as a horsetail. There is no other demantoid (or indeed other gemstone) which shows this horsetail feature.
 
The only disadvantageous property of demantoid is its low hardness figure at about 6.5 on the Mohs scale. It is the softest of the garnets, and is more suitable for use in brooches, pendants, or earrings, rather than rings, because of this.

In late Victorian times, and early in the twentieth century, demantoid became a very sought after stone. It commanded high prices because it has never been available in large quantity. In recent decades, it has been unobtainable as newly mined stones, and has only been available from antique jewellery.
 
The prices and value of Demantoid Garnet vary tremendously, depending on the size and quality of the gemstone. AJS Gems is your source for the highest quality colored stones from across the globe, available at Bangkok direct wholesale prices. Creating the finest jewelry starts with finding the best gemstones, and the best gemstones are found at AJS Gems.

 
Why Buy Loose Gemstones Instead of Pre-Set Jewelry?
 
There are many reasons, but basically it boils down to value and choice...

When buying your Demantoid Garnet gemstone loose instead of a pre-set stone, you can be sure you are getting the best value for your money.  Loose gemstones are less expensive, a better value, and you can really see what you are paying for.  The most important part of getting the right price and finding the best value is to first see what you're getting.  A jewelry setting will hide the inclusions inside a gem, and can deepen or brighten its color.  With a loose stone you can much more easily inspect the gem and see it for what it really is.  In this way you can get a better idea of its true worth and be sure you are paying a fair price.

The second advantage of buying a loose gemstone is choice.  You are free to pick the exact color, cut, shape and variety of the stone for the setting of your dreams, be it yellow gold, white gold, platinum or silver; prong set or bezel set with diamond accents.  You can experience the joy of creating your very own, one-of-a-kind jewelry design. Choose from a variety of jewelry settings and styles to create a completely original presentation that will perfectly suit your individual gemstone and will be as unique as you are!
 

Attributes


Origin The Bobrovka and Chusovaya River regions of Russia's Ural Montains.  Other sources include Namibia, Iran and Italy.
Color Light to deep green, yellowish green to golden brownish green
Refractive Index 1.888
Chemical Composition Ca3Fe2(SiO4)3
Hardness 6.5 - 7
Density 3.84
Crystal Structure Cubic
 
The demantoid belongs to the large gemstone family of the garnets, and is actually a variety of the garnet mineral andradite. But it is more than that: it is the most expensive kind of garnet and one of the rarest of all gemstones. It is highly esteemed on account of its rarity coupled with that incredible luminosity. For the latter, at least, there is a plausible explanation: the demantoid has an extremely high refraction (refractive index 1.880 to 1.889). Yet its high dispersion is also remarkable, in other words its ability to split the light which comes in through the facets and break it down into all the colors of the rainbow. The demantoid is a master of this, and does it even better than the diamond.  The refractive index (RI), measured using a refractometer, is an indication of the amount light rays are bent by a mineral. Birefringence is the difference between the minimum and maximum RI. When birefringence is high, light rays reflect off different parts of the back of a stone causing an apparent doubling of the back facets when viewed through the front facet.  Demantoid is singly refractive, and thus has no birefringence.

There are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, and uvarovite, grossularite, andradite, which are all calcium (metal) silicates.  In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.

Garnets as a group are relatively common in highly metamorphosed rocks and in some igneous formations. They form under the high temperatures and/or pressures that those types of rocks must endure. Garnets can be used by geologists as a gauge of how much temperature and pressure the rock has endured. Garnets are greatly variable in colors and varieties, though, and many of these are both rare and beautiful, producing genuinely precious gemstones. Some garnets are truly unique in the mineral kingdom and have much to offer as both gemstones and mineral specimens.

The general formula for most of the garnets is A3B2(SiO4)3. The A represents divalent metals such as calcium, iron, magnesium and/or manganese. The B represents trivalent metals such as aluminum, chromium, iron and/or manganese and in the rarer garnets; vanadium, titanium, zirconium and/or silicon. The general formula for a couple of rarer garnets (hibschite and katoite) is A3B2(SiO4)3-X(OH)4X. The main differences in physical properties among the members of the garnet group are slight variations in color, density and index of refraction.

Most gems have a crystalline structure. Crystals have planes of symmetry and are divided into seven symmetry systems. The number of axes, their length, and their angle to each other determine the system to which a crystal belongs.  Garnets are isostructural, meaning that they share the same crystal structure. This leads to similar crystal shapes and properties. Garnets belong to the isometric crystal class, which produces very symmetrical, cube-based crystals. The most common crystal shape for garnets however is the rhombic dodecahedron, a twelve sided crystal with diamond-shaped (rhombic) faces. This basic shape is the trademark of garnets, for no other crystal shape is so closely associated with a single mineral group like the rhombic dodecahedron is with garnets.

Most garnets are red in color, leading to the erroneous belief that all garnets are red. In fact a few varieties, such as grossular, can have a wide range of colors, and uvarovite is always a bright green. As a mineral specimen, garnets usually have well shaped and complex crystals and their color and luster can make for a very beautiful addition to a collection.


Why the Horsetail Influences the Value of a Demantoid

Demantoids from Namibia come in shades from a vivacious light green to an intense blue-green. They have a striking brilliance. Thanks to their hardness of just under 7 on the Mohs scale, they are well suited to being used in jewellery. However, they do lack one feature by which the rarest demantoid had always been able to be identified through the microscope: horsetail inclusions. These golden brown crystal threads of byssolite, mostly appearing to radiate out from the center of the stone, had previously occurred in almost all demantoids. But - more's the pity - they were missing in the relatively inclusion-free gems from Namibia. 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 as a rule inclusions, which can impair the transparency of a gemstone, are not a welcome sight. But with the demantoid's 'horsetail inclusions' it is a different matter. A beautiful, well formed byssolite horsetail inclusion can increase the value of the gemstone considerably, a good many collectors being prepared to pay a higher price.

Demantoid garnet inclusions

If you are offered a demantoid, it is definitely a good idea to have a look at it through under magnification. If the stone comes from Russia, you may be able to see these fine, fibrous byssolite wisps whose resemblance to a horsetail is unmistakable. If that is the case, you have a definite pointer to its origin. At the same time, this 'fingerprint of Nature' shows you that you are holding one of the rarest and most valuable gemstones in your hand. This rarity will also make itself felt in the price, since a horsetail demantoid from Russia will be valued much more highly than a green garnet from Namibia, however brilliant the latter may be.


Color                

The brilliant color of demantoid garnet is due to partial replacement of the silicate by chromic oxide. The spectrum of its colors includes many shades of green, from a slightly yellowish green to a brownish green with a golden glow. Particularly precious is a deep emerald green, though this only occurs very rarely indeed. It is not only fine and unusual, but the specimens are also mostly small, large ones being extremely rare. Once cut, only a few stones weigh more than two carats, and most of them hardly exceed one. And even if you come across one set in a piece of jewellery, it is always likely to be a small stone.

While the color of demantoid never equals that of the finest emerald, an emerald-green is the ideal. The color should be as intense as possible, without being overly dark or yellowish green.  It should be noted that demantoid’s fire is best seen in the lighter, less saturate gems. Thus the color preference is a matter of individual taste. Some people will choose an intense body color and less fire, while others prefer a lighter body color and more fire.


Cut 

In the market, demantoids are found mainly as round brilliant or cushion cuts. Cabochon-cut demantoids are not often seen.
 
The lack of pleochroism means that orientation is not a problem and the equidimensional shape of the rough generally provides good yields from rough to cut.


Treatments
 
Some demantoid garnet is heat-treated to improve the color. The resulting stones are stable under normal wearing conditions.
 
AJS Gems fully discloses any and all treatments to our gemstones.
 

Sources

Andradite commonly occurs in contact metamorphic deposits, resulting from metamorphism of impure limestones. It also is found in some metasomatic skarn deposits. Demantoid occurs mainly in serpentinites and chlorite schists.
 
The original locality for demantoid was in Russia’s Ural Mountains. Today, deposits of lesser material exist in Iran, Italy and Namibia, but the Russian material remains the standard by which the gem is judged.
 
After its discovery in 1868 in Russia's Ural mountains, the demantoid rapidly proceeded to become a much desired gemstone. Comet-like, it scintillated among the finest jeweller's workshops in Paris, New York and St. Petersburg. First and foremost, Russia's star jeweller Carl Faberge adored it for its tremendous brilliance and loved to incorporate it in his precious objects. But with the chaos of the First World War, the green star began to fade rapidly. Now, it made only rare appearances in the gemstone trade, and when it did so it was mostly incorporated in an item of second-hand jewellery, or among remnant stocks from the places where it had originally been found in the Urals. Occasionally demantoids were found in other parts of the world, for example in the Congo, or in Korea in 1975, but the quality of these stones was such that they were suitable for collectors' use only.

The situation changed quite suddenly in the middle of the 1990s, when a new seam bearing gemstones was discovered in Namibia. Demantoid was among them.
 
Demantoids from Namibia show good color and brilliance, however, they lack one minor characteristic: the so-called "horsetail-inclusions”, fine bushy-shaped inclusions which are the characteristic birthmark identifying Russian Demantoids.
 
Recently, small finds have again been made in Russia, and a small quantity of fine quality stones have recently come onto the market.  Gemstone lovers wishing to acquire a piece of demantoid garnet should take this opportunity to do so. If the current seams of demantoid run out, there may be another century without new stocks of demantoid becoming available.
 
 
Mythology
 
Throughout time, there have been many ancient traditions and legends about the gemstone garnet...

Garnets have been known to Man for thousands of years. Noah, it is said, used a finely cut, glowing garnet within a lantern to help him steer his ark through the dark night.

Many an early explorer and traveler liked to carry a garnet with him, for the garnet was popular as a talisman and protective stone, as it was believed to light up the night and protect its bearer from evil and disaster.

The name “garnet” comes from the Latin word “Garanatus,” meaning “seedlike,” in reference to a pomegranate. This reference makes sense as small garnets look like the bright red seeds you find inside in a pomegranate.

In medieval times, garnets were thought to cure depression, protect against bad dreams, and relieve diseases of the liver, as well as hemorrhages.

Hebrew writers include the garnet as one of the twelve gems in Aaron’s breastplate.

Christian tradition considered the blood-red garnet as a symbol of Christ’s sacrifice.

The Koran holds that the garnet illuminates the Fourth Heaven of the Moslems.

The Greeks said garnet guarded children from drowning. It was also thought to be potent against poisons.

Garnets were found as beads in a necklace worn by a young man in a grave that dates back to 3000 B.C. This is proof of the hardness and durability of the stone.

Plato had his portrait engraved on a garnet by a Roman engraver.

Garnet is the Birthstone for the month of January and the stone that celebrates the 2nd anniversary of marriage.
 
 
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