Demantoid Garnet Value, Price, and Jewelry Information


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

Demantoid is the green-colored variety of andradite garnet. Discovered in Russia in the early 19th century, demantoid was identified as a variety of andradite in 1854 by noted mineralogist Nils Gustaf Nordenskiöld. Russia was long the only source of this rarest of garnets. Supply was so low, demantoids were usually seen only on antique jewelry pieces. Since the 1990s, new sources have been discovered, and the gem remains a desirable, but very expensive, jewelry stone.

Demantoid Value

Even with new sources, demantoid remains very rare. Clean, facetable stones command very high prices per carat. Faceted stones greater than 1 carat are rarely seen.

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

See the entire Gem Price Guide.

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Demantoid Information

DataValue
NameDemantoid
Is a Variety ofAndradite
Crystallography Isometric
Refractive Index 1.881-1.888
Colors Yellow-green, green, deep green
Luster Adamantine
Fracture Conchoidal
Hardness 6.5-7
Toughness Good
Specific Gravity 3.82-3.88 (San Benito, CA demantoid: 3.81)
Cleavage None
Dispersion 0.057
Heat SensitivityYes
Luminescence None
Spectral A strong band is visible at 4430, cutoff at the violet end of the spectrum. Chromium spectrum is visible, with a doublet at 7010, sharp line at 6930, and two bands in the orange at 6400 and 6220. Demantoid is red in the Chelsea filter.
Wearability Good
Transparency Transparent
Phenomena Occasional chatoyancy due to byssolite inclusions.
Birthstone January (Garnet)
FormulaCa3Fe2Si3O12, chromium (Cr) traces cause green color, ferric iron (Fe3+) traces cause yellow color.
Pleochroism None.
EtymologyAfter the old German demant for “diamond,” due to the stone's high dispersion.
OccurrenceSchists and serpentine rocks; metamorphosed limestones and contact zones.
Inclusions Horsetail inclusions of byssolite (fibrous amphibole).
Demantoid Garnet - Faceted Set
Demantoid (Andradite Garnet): Russia (1.93, 0.93, 4.37). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Comments

The exceptional brilliance and dispersion of the demantoid inspired Nordenskiöld to name this stone “diamond-like.” Nevertheless, this garnet gem has greater brilliance and a higher dispersion than its diamond namesake. It’s also far more brilliant than other well-known green gemstones such as emerald, peridot, and fellow garnet tsavorite. The dispersion can be masked by dark body color, but small, light-colored gems 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 brooch-pendant,” Moscow 1899-1908, Collection V. Kirichenko, by Shakko. Licensed under CC By-SA 3.0.

Identifying Characteristics

Horsetail inclusions of byssolite (fibrous amphibole) are diagnostic for this gem. The “horsetails” usually have a golden color. These inclusions occasionally produce chatoyant or cat’s eye gems.

Synthetics

Demantoid has not been synthesized. However, green glass as well as green yttrium aluminum garnet (YAG), a synthetic garnet, have been used as simulants.

Enhancements

Heat can be used to improve color. This is a stable and undetectable treatment.

Demantoid Garnet Madagadcar
“Garnet var. Demantoid,” Madagascar. © Rob Lavinsky, www.iRocks.com. Used with permission.

Sources

  • Russia: the Ural Mountains region; Koryakskoe plateau; Kola Peninsula.
  • Namibia: a commercially important source since 1996.
  • Madagascar: a commercially important source since 2009.
  • Italy: Ala, Piedmont, a source of dark apple-green demantoids.
  • United States: San Benito County, California, unusual cat’s eye material.
  • Afghanistan; Azerbaijan, Canada; Iran; Pakistan; South Korea; Sri Lanka; Zaire.
Andradite Demantoid Namibia
“Andradite (Var: Demantoid),” Tubussis 22 farm, Karibib District, Erongo Region, Namibia. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

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

The Smithsonian Institution, Washington DC, has a faceted 11.24-carat gemstone on display.

Trade Names

Demantoids have been called “Siberian emeralds,” “Siberian chrysolites,” and “Ural chrysolites.” Of course, garnets are chemically and optically distinct from these gem species. Consult our article on false or misleading gemstone names for more examples from the garnet family.

Demantoid
“Demantoid, Bobrowa-Fluss/Ural, Mineralogisches Museum Bonn” by Elke Wetzig. Licensed under CC By-SA 3.0.

Care

Heat sensitive garnets should be cleaned with warm water, detergent, and a soft brush. Avoid mechanical cleaning and exposure to extreme heat. Consult our gemstone care guide and jewelry cleaning guide for more information.

Demantoid Garnet Brooch
Demantoid (Andradite Garnet): Russia (Stones ~ 0.25-0.50). Photo © Joel E. Arem, PhD, FGA. Used with permission.