Green Demantoid Garnet, in the Andradite (ANN-druh-dite) mineral species belonging to the Garnet group, is one of the rarest of Garnets.
Discovered in Russia in 1868, the supply was consumed in jewelry by 1896. Production now is limited to a few stones a year. Utilized in Art Nouveau jewelry during the turn of the century. Demantoid is important to Gem aficionados for four reasons: its great rarity, its color, its high dispersion and its distinctive inclusion. Dispersion, or the breaking of White light into spectral colors, is measured at 0.044 for Diamond and 0.057 for Demantoid. Demantoid's name means "diamond" in German, an indication of its beautiful luster. Demantoid deposits of lesser material exist in San Bonito County, California, the Piedmont area of Italy, Iran, Nambia, Korea, the Congo and the Stanley Butts area of Arizona, but because the original locality for demantoid was in Russian Ural Mountains, the Russian material remains the standard by which the gem is judged.
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. Many stones are in the yellowish-Green range with lesser qualities being brownish Green of grayish Green. The color of demantoid is believed to be due to chromium. It should be noted that the fire in a demantoid is best seen in the lighter, less saturated gems. Thus 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. Demantoid garnet generally looks best under daylight. Incandescent light makes it appear slightly more yellowish-green.
Because of its high dispersion, demantoid looks great in the same type of lighting as diamond, i.e., multi-point (as opposed to diffuse) lighting. Demantoid is relatively clean, thus when buying one you should look for an eye-clean or near-eye-clean stone.
Demantoids exhibit a unique Byssolite inclusion called a "horse tail." This inclusion is formed by Asbestos, needle-like fibers which radiate from a central crystal, usually Chrysolite, in a curving style similar to a horse's tail. Gem cutters often fashion a Demantoid to better show the inclusion since this is a definite characteristic of a Demantoid.
Generally you will only find round brilliant, oval, or cushion cuts. Typically crystals are small and not plentiful, generally under 1 Carat. Demantoid is rare in faceted stones above 2 carats. Fine demantoids above 5 carats can be considered world-class pieces.
Demantoid is among the most expensive of all garnets, but like all gem materials, low-quality (i.e., non-gem quality) pieces may be available for a few dollars per carat. Prices for demantoid vary greatly according to size and quality, but top gem quality stones with no enhancement may reach as much as $10,000 per carat.
Demantoid Garnet is a highly valued Collectors Gemstone.
TREATMENTS - Demantoid Garnet is typically not treated in any way. In recent years, however, some of the lesser quality demantoid garnet has been discovered to have been subjected to heat treatment, primarily to improve the color, and the resulting stones are stable under normal wearing conditions. There's no need to worry when you see heat enhancement disclosed, however, any type of treatment performed on a gemstone usually does affect it's value. A natural non-treated or untreated gem is always more desirable, therefore will carry a higher premium.
The following links are to reputable Gem Laboratories and Appraisers :
CARE - It is usually safe to clean Demantoid Garnet in an UltraSonic Cleaner, and extremely risky to use a steamer. We recommend using an Ionic Cleaner and/or warm soapy water and a soft brush as the best way to clean your Demantoid.
We only feature and offer Natural Demantoid Garnets. The rarity, beauty, and of course the horsetail inclusion, is reason enough for owning this Gem.