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Demontoid Garnet

Historical values 2005 - 2016

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About Demantoid Garnet - History and Introduction

Demantoid garnet is a brilliant green variety of andradite garnet, coloured by chromium and ferric iron. It is considered to be the rarest and most valuable member of the garnet group of minerals. Demantoid has an exceptionally high refractive index making it not only the most brilliant garnet but also more brilliant than both ruby and sapphire. Demantoid garnet also has exceptional fire and boasts the highest dispersion rating of any jewelry gemstone available today, even exceeding that of fine diamond. Like most green garnets, demantoid is typically found only in small sizes. Specimens over one carat are rare and specimens over 2 carats are very rare indeed. In fact, demantoid garnet is traditionally considered to be one of the rarest colored gemstones today.

Demantoid garnet was first discovered in the Ural Mountains of Russia, and although garnets have been known for ages, demantoid wasn't discovered until 1853. Today, Russian demantoid is considered extremely rare and very valuable. Russian demantoid is highly prized for its distinctive golden 'horsetail' inclusions, owed to the presence of byssolite or chrysotile asbestos; but not all Russian demantoid exhibits golden thread-like inclusions. Other origins, may also produce similar inclusions but rather than being caused by traces of asbestos, they are regarded as characteristics of serpentinite geographic origins.

Identifying Demantoid Garnet

Demantoid belongs to the andradite variety of garnet and can be identified by its calcium iron silicate content. It has specific gravity (density) ranging from 3.7 to 4.1 and an extremely high refractive index of 1.88 to 1.94 (higher than sapphire and ruby). Demantoid is the most brilliant of all garnets, with only diamond and some zircon having greater brilliance than demantoid. Demantoid garnet has a dispersion that exceeds diamond and an adamantine (diamond-like) luster. Demantoid is coloured by chromium and ferric iron. It rarely occurs in large sizes, which can help identify it from other similar gems such as peridot, grossularite, spinel, emerald, tourmaline or uvarovite garnet.

Demantoid Garnet Origin and Gemstone Sources

Demantoid garnet was first discovered in the Ural mountains in Russia in 1853; the Russian deposits remained the only source until a major find was discovered in Namibia (the Green Dragon Mine) in 1996. In 2003, there was another significant deposit discovered in Madagascar. More recently, there have been reported findings in Afghanistan, Italy, Iran, China, Korea, Zaire and the USA.

Buying Demantoid Garnet and Determining Demantoid Garnet Gemstone Value Back to Top

Demantoid Garnet Colour

Demantoid garnet by definition is always green, its characteristic colour is caused by traces of chromium. The yellowish colours are owed to ferric iron. Colours range from a light yellowish-green (similar to peridot) to a deep green, almost the colour of fine emerald. Specimens with a more intense green are more highly valued, but the lighter stones display substantially more fire.

Demantoid Garnet Clarity and Luster

Demantoid garnet is known for its high transparency and adamantine (diamond-like) luster. Inclusions are common for demantoid garnet, especially in stones weighing over 1 carat. Eye-clean stones of under 1 carat weight can be found but most will have some visible inclusions. With Russian demantoid, horsetail inclusions are welcomed as a desirable characteristic.

Demantoid Garnet Cut and Shape

Demantoid garnet is typically faceted rather than cut en cabochon. The most common shape is oval as it preserves the most original rough carat weight, which is especially important since most stones are quite small. Other popular shapes include round, pear, cushion and fancy cuts. Diamond-cut stones are quite popular due to their ability to maximize demantoid's remarkable brilliance and fire.

Demantoid Garnet Treatment

Like most garnet varieties, demantoid garnet is not known to be treated or artificially enhanced in any way. In 2003, rumours circulated that some Russian material may have been enhanced through low heating, but gemological tests were unable to detect the treatment.

Color

Color Description; Occurrence

1 ct.

3 ct.

5 ct.

10 ct.

30 ct.

090 - Dark Green

Alternative name, occurrence category: Andradite. Rare

1,488.93

3,383.94

5,278.95

No data

No data

088 - medium dark Green; strong

Alternative name, occurrence category: Andradite. Rare

1,789.89

4,067.93

6,345.97

No data

No data

086 - medium Green; very slightly greyish

Alternative name, occurrence category: Andradite. Rare

1,672.22

3,800.51

5,928.79

No data

No data

077 - medium slightly yellowish Green; very slightly greyish

Alternative name, occurrence category: Andradite. Rare

932.28

2,118.82

3,305.36

No data

No data

075 - medium light slightly yellowish Green; very slightly greyish

Alternative name, occurrence category: Andradite. Common

601.91

1,367.98

2,134.04

No data

No data

069 - medium yellowish Green; slightly greyish

Alternative name, occurrence category: Andradite. Common

634.72

1,442.55

2,250.37

No data

No data

057 - medium light greenish Yellow, very slightly greyish

Alternative name, occurrence category: Andradite. Common

209.31

475.71

742.10

No data

No data

093 - light very slightly bluish Green; very slightly greyish

Alternative name, occurrence category: Andradite. Rare

1,132.54

2,573.96

4,015.37

No data

No data

About Demantoid Garnet - History and Introduction

Top

Demantoid Garnet

Colour: green, yellowish green

Hardness: 6.5

Refractive index: 1.88 - 1.89

Density: 3.82 - 3.85

Chemical composition: Ca3Fe2(SiO4)3

Crystal structure: isometric

Origins: Russia, Namibia, South Africa.

Demantoid is a rare and expensive green variety of garnet andradite. The best stones come from the Ural Mountains in Russia. Peculiar 'horse tail' inclusions of byssolite are appreciated by collectors, and will increase the stone's value. Demantoids are generally not treated.