Demantoid

“By mineralogists it has been termed Dentantoid, and by Russian jewellers it is often called ‘Siberian Chrysolite’, or Olivine. I am sorry to say it has been sold in England as Olivine, at as high a price as £5 per carat.”

Edwin Streeter, Precious Stones and Gems (1898)

Etymology

Demantoid or Demantoid Garnet was first discovered in 1849 and named in 1855 by Dr Nordenskjöld, who also gave it the name Alexandrite. Dr Nordenskjöld derived the name from the old German word “demant” (similar to Diamond), due to its adamantine sheen, its extreme sparkle and a fire (also referred to as ‘dispersion’, or the fractioning of light into its component colors) superior even to Diamond. Although Nordenskjöld did not correctly identify its family heritage, Demantoid was known by a large variety of common and incorrect names in the era following its discovery: Bobrovka Garnet, Siberian Chrystolite, Ural Chrysolite, Ural Pearl and Uralian Emerald. Fortunately, in 1871, Russian mineralogist V.P. Yeremeev cleared the confusion, confirming Demantoid as a green variety of Andradite.

A large specimen of ambandja dematoid

A large specimen of Ambandja Dematoid

Chemical composition of Demantoid

Demantoid is a calcium Garnet variety of Andradite and, together with Grossular Garnet - also known as Tsavorite, is an important member of the green Garnet family. Garnets are a group of idiochromatic minerals with similar crystalline structure but varying composition; they exist in a variety of colors: chocolate, green, orange, pink, purple, red, yellow and blue.

Demantoid extraction

At one point, Demantoid was believed to remain a relic of the past, but the reestablishment of small-scale mining activities in Russia in 1991, and the discovery of new deposits in other countries, renewed the interest in the manifold attractions of this gem. Demantoid is now extracted in Iran, Italy, Madagascar, Mozambique and Namibia, even though its Russian varieties - which are the most intense and pure green - remain the gold standard for the market. Variation in color between deposits depends on chromium levels or, as is the case for Madagascar Demantoid, its complete absence. Note that all of the mines mentioned produce true Demantoid: all green Andradite is Demantoid, based on the scientific explanation of the color. While the fall of the Soviet Union saw the renewed development of many of the original deposits in the Urals, new deposits of Russian Demantoid were discovered in the 1990s, including those at Karkodino, Kamchatka, Chukotka and various other small deposits in the Novouralsk region.

Another example of Ambandja Dematoid

Another example of Ambandja Dematoid

The history of Demantoid

Due to its similar color, Demantoid was initially mistaken for Emerald, and for a while was erroneously sold as Chrystolite. Deriving its name from a Greek term meaning ‘golden gemstone’, Chrystolite is the ancient name for Peridot (a variety of Fosterite-Fayalite series in the Olivine mineral group). When Demantoid was originally introduced into the precious gemstone market, its spectacular beauty assured immediate success. As the star of exclusive Victorian-era jewelry, Demantoid was a spectacular success in its homeland, Czarist Russia. It quickly became one of the most commonly used gemstones by the jewelers of the Czar’s court between the late 19th and early 20th century. Demantoid was also the favorite gemstone of the famous Russian goldsmith Peter Carl Fabergé (1846 - 1920), creator of the fabulous golden eggs encrusted with precious stones. The sovereignty of Demantoid also extended to other realms; it gained favor among the grand masters of French fashion, and even the legendary George Frederick Kunz (head gemologist at Tiffany & Co) was sent to Russia to buy all the Demantoid he could get his hands on. However, Russia was about to undergo major changes. Lenin had returned from his exile, the revolution had been unchained, and bourgeois luxuries such as gemstones were immediately banned. Without warning, demand waned, and a once highly desired gemstone became no more than a note in the margins of history. Today, Demantoid continues to be extracted from a variety of sources, but remains difficult to source due to both the difficulty of its extraction and being a gemological rarity.

Demantoid was the favorite gemstone from Peter Carl Fabergè (1846-1920), the Russian jeweler particularly well known for his Imperial Fabergè Easter Eggs

Demantoid was the favorite gemstone from Peter Carl Fabergè (1846-1920), the Russian jeweler particularly well known for his Imperial Fabergè Easter Eggs.

Properties of Demantoid

Like Emeralds, Demantoid owes its color to chrome and/or iron and varies from bright green (forest green) and yellowish-green (grass green) to yellow-green (Savannah or canary green), and even bluish-green and gray-green varieties may be found in Africa. In Andradite, iron is responsible for the yellow color, but when replaced by chrome, the gem reveals various shades of green. If the Demantoid retains traces of iron, this results in a yellow or yellowish green color. In essence, the more yellow Demantoid is, the more iron it contains within its crystalline structure. As is the case for many colored gemstones, the ideal lies half-way, and in case of Demantoid, this usually means an intense ‘emerald green’. Although the Emerald is the standard reference when classifying green gemstones, in the case of Demantoid, a judgment on color alone is not enough, as other factors must be considered, such as adamantine luster and extreme sparkle. An additional optical property that presents itself is fire: Demantoid is actually the Garnet with the most fire of all, with a dispersion of 0.057, greater even than that of Diamond (0.044). Fantastic fire in a gem increases its beauty and value, giving exceptionally brilliant examples a unique light. On average, Demantoid looks best in daylight, but as it contains both iron and chrome, appears different under different lighting; more yellowish in incandescent lighting, but this slight shift is always pleasing to the eye, accenting the distinct personality of this gemstone. GIA classifies Demantoid as a Type II gemstone (a few minor inclusions may be visible to the naked eye), but the market standard is eye-clean.

In reality, Demantoid stones over half a carat are not usually eye-clean, and the majority of extracted gemstones are smaller than one carat. Demantoids weighing 1 to 2 carats are exceptional, and any example larger than 5 carats is museum quality. European and African Demantoid may be distinguished based on subtle fibrous inclusions that are present in a ‘horsetail’ pattern. These subtle chrysolite needles form brush-stroke inclusions, often with very small chromite crystals at their core. Namibian and Madagascar Demantoid do not display this horsetail patterning. Horsetail inclusions are sometimes desirable, but as is the case with the choice between color and fire, this remains a matter of personal preference. As Demantoid is a very rare and expensive Garnet, it is important to make sure that any inclusions present, horsetail or otherwise, not negatively affect your perception of beauty.

Demantoid in all of its beauty

Demantoid in all of its beauty

Varieties of Demantoid

In addition to the famed Russian Demantoid, which sets the color standard for the market and remains extremely rare to this day, wonderful examples are also available from Namibia: their uniqueness lies in their color, a light green compared to Russian Demantoid due to the smaller amount of chromium present in its Chemical composition, but with great brilliance. Italian Demantoid entered the market in the 1970s, joined by Iranian Demantoid in 2002. Recently, Demantoid has also been discovered in Madagascar; originally mistaken for Green Sapphire or Green Zircon, the extraction of the Demantoid only began in 2009, though it was first discovered there in 1922.

Care for Demantoid

Demantoid may be damaged by major thermal changes; therefore, it should not be exposed to drastic temperature shifts, such as steam or ultrasound cleaning.