Demantoid Garnet Value, Price, and Jewelry Information

Modified square/cushion-cut demantoid garnet, 1.88 cts, 6.0 x 6.0 x 5.0 mm, Antetezambato, Ambanja District, Antsiranana Province, Madagascar. © Rob Lavinsky, www.iRocks.com. Used with permission.

Demantoid Garnet

One of the rarest garnet varieties, demantoid can have a green color that rivals emerald and a fire that exceeds diamond. Demantoids are highly prized by both gem collectors and jewelry enthusiasts.

Demantoid Garnet Value

Even with the discovery of new sources since the 1990s, demantoid remains very rare. It’s the most well-known andradite garnet and one of the most valuable garnets of any variety. Clean, facetable stones command very high prices per carat. However, demantoids with horsetail inclusions — wavy, golden, and fibrous — are especially coveted by collectors.

oval-cut demantoid - Russia

Brilliant, oval-cut demantoid with horsetail inclusions, 2.67 cts, 8.27 x 6.81 x 5.71 mm, Ural Mountains, Russia. © Rob Lavinsky, www.iRocks.com. Used with permission.

For more information on value and quality factors for demantoids, consult our buying guide.

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Garnet Value via Gem Price Guide

Top Color: oR, R, PR, rP 6/4
Almandine All sizes
to /ct
Fine Color Andradite: G 5/4
Andradite All sizes
to /ct
Chrome Pyrope All sizes
to /ct
Color Change .5 to 1 carat 1 to 6 carats
Africa to /ct to /ct
US to /ct to /ct
Demantoid to 1 carat 1 to 3 carats
to /ct to ,000/ct
Grossular Garnet .5 to 1 carat 1 to 5 carats 5 carats plus
Mint Green (Merelani) to /ct to /ct to /ct
Yellow/Orange to /ct to /ct to /ct
Yellow/Green to /ct to /ct to /ct
Other colors /ct /ct to /ct
Fine Color Hessonite: yO 4/5
Hessonite Garnet All sizes
to /ct
Malaya Garnet .5 to 1 carat 1 to 5 carats 5 carats plus
to /ct to /ct to /ct
Mozambique All sizes
to /ct
Mali Garnet All sizes
to /ct
Fine Color Spessartite: O 4/5
Mandarin Orange All sizes
to /ct
Fine Color Pyrope: R 6/5
Pyrope 1 carat plus
/ct
Fine Color Rhodolite: rP, PR 6/5
Rhodolite .5 to 1 carat 1 to 10 carats 10 carats plus
Faceted to /ct to /ct to /ct
Cabochons to /ct to /ct to /ct
Spessartite Reds See Mandarin above .5 to 3 carats 3 to 6 carats
Little 3 Mine to /ct to /ct
African to /ct to /ct
Darker reds to /ct
Star Garnet All sizes
6 ray star to /ct
4 ray star to /ct
Fine Color Tsavorite: G 6/5
Tsavorite .5 to 1 carat 1 to 2 carats 2 carats plus
Faceted to /ct to /ct to ,000/ct
Uvarovite 10 carats plus
Druzy to /ct
Cabochons All Sizes
Common red to purple to /ct

Demantoid Garnet Information

Data Value
Name Demantoid Garnet
Is a Variety of Andradite
Colors Yellow-green, green, deep green
Crystallography Isometric
Refractive Index 1.881-1.888
Luster Adamantine.
Hardness 6.5-7
Wearability Good
Fracture Conchoidal
Specific Gravity 3.82-3.88 (San Benito, CA demantoid: 3.81)
Birefringence None.
Cleavage None
Dispersion 0.057
Heat Sensitivity Yes
Luminescence None
Luminescence Present No
Enhancements Heat treatment.
Typical Treatments Heat Treatment
Transparency Transparent.
Absorption Spectrum Strong band visible at 4430, cutoff at violet end of the spectrum. Chromium spectrum visible, with a doublet at 7010, sharp line at 6930, and two bands in orange at 6400 and 6220. Demantoid is red in the Chelsea filter.
Phenomena Occasional chatoyancy due to fibrous inclusions.
Birthstone January
Formula

Ca3Fe2Si3O12, chromium (Cr) traces cause green color, ferric iron (Fe3+) traces cause yellow color.

Pleochroism

None.

Optics

Isotropic. May show anomalous birefringence.

Etymology

After the old German demant for “diamond.”

Occurrence

Schists and serpentine rocks; metamorphosed limestones and contact zones.

Inclusions

Horsetail inclusions of byssolite (fibrous amphibole) or chrysotile.

Demantoid Garnet - Faceted Set

Demantoid (andradite garnet): Russia (1.93, 0.93, 4.37). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Comments

Demantoid was discovered in Russia in the early 19th century. In 1854, the noted mineralogist Nils Gustaf Nordenskiöld identified this gem as a variety of andradite garnet. These stones had such exceptional brilliance and dispersion or “fire” that they inspired Nordenskiöld to name demantoid after its “diamond-like” appearance.

In fact, this garnet has greater brilliance and a higher dispersion than its diamond namesake as well as other well-known green gemstones, such as emerald and peridot. Although dark body colors can mask their dispersion, small demantoids with light colors are quite dazzling.

Demantoid was a popular gemstone during the Belle Époque period (1890-1915), especially in Art Nouveau jewelry. The Russian Czars particularly favored this gem.

Demantoid Brooch Pendant

Demantoid and diamond brooch-pendant, Moscow (1899-1908), collection V. Kirichenko. Photo by Shakko. Licensed under CC By-SA 3.0.

Russia was long the only source of demantoids, but supplies ran so low, these gems were usually seen only in antique jewelry pieces. However, since the 1990s, new discoveries in Namibia, Madagascar, and other locations, as well as renewed mining in Russia, have made the gem more available. Today, demantoids are still desirable, but very expensive, jewelry stones.

3.80-ct demantoid - Namibia

3.80-ct demantoid, clarity VVSI, sourced near Karibib, Namibia. Photo © Claradyn Venter. Used with permission.

Identifying Characteristics

Horsetail inclusions of byssolite or chrysotile, usually golden in color, are named after their long, wavy appearance. These inclusions have long been considered diagnostic for identifying demantoids. However, a 2018 study found horsetail inclusions in non-demantoid (brown) andradite. Thus, horsetails may not be sufficient in and of themselves for identifying demantoids, nor do all demantoids have horsetails.

0.38-ct demantoid with horsetail inclusions - Russia

Russian demantoid with horsetail inclusions, 0.38 cts, 4.3 x 3 mm. Photo courtesy of liveauctioneers.com and Jasper52.

Inclusions in demantoids may rarely produce cat’s eye gems.

Although demantoids may have an emerald-like color and included appearance, the optical and physical properties of these two distinct gem species differ considerably. Most visibly, demantoids have greater dispersion and no birefringence. (Note that some demantoids may show anomalous birefringence. A polariscope examination can help determine if a stone is truly birefringent).

Demantoid Garnet Madagadcar

Garnet on matrix (demantoid variety), 2.8 x 2.4 x 1.5 cm, Madagascar. © Rob Lavinsky, www.iRocks.com. Used with permission.

Like demantoids, tsavorites and uvarovites are rare garnet varieties with emerald-like color. However, the specific gravity (SG) and dispersion of demantoid exceed that of its green garnet brethren.

Synthetics

Demantoid hasn’t been synthesized, but green glass as well as green yttrium aluminum garnet (YAG), a synthetic garnet, have been used as simulants.

Enhancements

Heating may improve demantoid color. This is a stable and undetectable treatment.

Sources

Historically and currently, Russia has been an important producer of demantoids. Notable gem sources include the Ural Mountains region, the Koryakskoe plateau, and the Kola Peninsula.

Since 1996 and 2009, respectively, Namibia and Madagascar have become commercially important sources.

2.15-ct demantoid - Namibia

2.15-ct demantoid, clarity IF, sourced near Karibib, Namibia. Photo © Claradyn Venter. Used with permission.

In Italy, Ala, Piedmont produces dark, apple-green material. Val Malenco, Sondrio Province also produces demantoids.

demantoid crystals in asbestos matrix - Italy

This specimen features about a dozen demantoids on a fibrous asbestos matrix. The largest crystal measures about an inch across. 5.5 x 3.7 x 1.2 cm, Val Malenco, Sondrio Province, Lombardy, Italy. © Rob Lavinsky, www.iRocks.com. Used with permission.

Other notable sources of gem-quality demantoids include the following:

  • Afghanistan; Azerbaijan; Canada; Democratic Republic of the Congo; Iran; Mexico; Pakistan; South Korea; Sri Lanka; San Benito County, California, United States.
demantoid - Iran

Andradite (variety demantoid), 3.0 x 2.7 x 2.4 cm, Belqeys Mountain, near Takab, West Azerbaijan, Iran. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

Demantoids are typically small stones. Stones larger than 10 carats are very rare. Faceted stones greater than 1 carat are rarely seen. The largest demantoid ever found hailed from the Russian Urals and weighed 252.5 carats or 50.5 grams.

The Smithsonian Institution has a faceted 11.24-carat specimen on display.

trilliant-cut demantoid - Madagascar

Modified trilliant-cut andradite (demantoid), 2.03 cts, 12.0 x 9.0 mm, Antetezambato, Ambanja District, Antsiranana Province, Madagascar. © Rob Lavinsky, www.iRocks.com. Used with permission.

Trade Names

Consumers may encounter demantoids offered for sale under such names as “Siberian emeralds,” “Siberian chrysolites,” and “Ural chrysolites.” Of course, garnets constitute a distinct group of gem species from emeralds. “Chrysolite” is an archaic term for green to yellow-green gems that has been applied to peridots as well as chrysoberyls and prehnites. All of these gems also constitute species distinct from demantoids.

For more examples of false or misleading gemstone names, consult this article.

Demantoid crystals - Russia

Demantoids from the Bobrovka River, Russia, on display at the Mineralogical Museum, Bonn, Germany. Photo by Elke Wetzig. Licensed under CC By-SA 3.0.

Care

Heat sensitive garnets, like demantoids, should be cleaned with warm water, detergent, and a soft brush. Avoid mechanical cleaning and exposure to extreme heat.

Some demantoids may have a hardness of 6.5, which means they are somewhat susceptible to scratching. Therefore, use protective settings for these gems, especially if used as ring stones.

Consult our gemstone care guide and jewelry cleaning guide for more information.

Antique demantoid beetle pin

This antique beetle pin, circa 1870, features demantoids and diamonds, red garnets for the eyes, and unparalleled 14k craftsmanship. Russian demantoids ~ 0.25-0.50 cts. Photo © Joel E. Arem, PhD, FGA. Used with permission.