Andradite Value, Price, and Jewelry Information


andradite
By Parent Géry (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

Andradite is one of the rarest and most sought after garnets. There are no major sources of andradite and the supply is limited to small deposits.

Andradite Value

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
AlmandineAll sizes
to /ct
Fine Color Andradite: G 5/4
AndraditeAll sizes
to /ct
Chrome PyropeAll sizes
to /ct
Color Change.5 to 1 carat1 to 6 carats
Africa to /ct to /ct
US to /ct to /ct
Demantoidto 1 carat1 to 3 carats
to /ct to ,000/ct
Grossular Garnet .5 to 1 carat1 to 5 carats5 carats plus
Mint Green (Merelani) to /ct to /ctto /ct
Yellow/Orange to /ctto /ctto /ct
Yellow/Green to /ctto /ctto /ct
Other colors/ct/ct to /ct
Fine Color Hessonite: yO 4/5
Hessonite GarnetAll sizes
to /ct
Malaya Garnet.5 to 1 carat1 to 5 carats5 carats plus
to /ct to /ctto /ct
MozambiqueAll sizes
to /ct
Mali GarnetAll sizes
to /ct
Fine Color Spessartite: O 4/5
Mandarin OrangeAll sizes
to /ct
Fine Color Pyrope: R 6/5
Pyrope1 carat plus
/ct
Fine Color Rhodolite: rP, PR 6/5
Rhodolite.5 to 1 carat1 to 10 carats10 carats plus
Faceted to /ct to /ctto /ct
Cabochons to /ct to /ctto /ct
Spessartite Reds See Mandarin above.5 to 3 carats3 to 6 carats
Little 3 Mine to /ct to /ct
African to /ct to /ct
Darker reds to /ct
Star GarnetAll sizes
6 ray star to /ct
4 ray star to /ct
Fine Color Tsavorite: G 6/5
Tsavorite.5 to 1 carat1 to 2 carats2 carats plus
Faceted to /ct to /ct to ,000/ct
Uvarovite10 carats plus
Druzy to /ct
CabochonsAll Sizes
Common red to purple to /ct

See the entire Gem Price Guide.

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Andradite Information

DataValue
NameAndradite
Is a Variety ofGarnet
VarietiesDemantoid, Melanite, Topazolite
Crystallography Isometric
Refractive Index 1.855-1.95
Colors Green, yellowish green, yellow, brown, black
Luster Vitreous to resinous.
Fracture Conchoidal
Hardness 6.5 - 7
Specific Gravity 3.70- 4.10; melanite about 3.9; demantoid 3.82-3.88.
Birefringence None.
Cleavage None
Dispersion 0.057
Heat SensitivitySome
Luminescence None
Transparency Translucent to transparent.
Absorption Spectrum A strong band is visible at 4430, cutoff at the violet end of the spectrum. Sometimes (in demantoids) the Cr spectrum is visible, with a doublet at 7010, sharp line at 6930, and 2 bands in the orange at 6400 and 6220. Demantoid is red in the Chelsea filter.
Birthstone January (Garnet).
FormulaCa3Fe2Si3O12
Pleochroism None.
Optics Isotropic, may show anomalous birefringence.

Andradite is named after the Portuguese mineralogist, d’’Andrade.

Melanite has 1-5% Ti oxide; schorlomite is rich in Ti also; topazolite from Italy is yellowish-green; demantoid is rich green, colored by Cr.

This is one of the rarest and most sought after garnets. There are no major sources of andradite and the supply is limited to small deposits.

Andradite occurs in schists and serpentine rocks (demantoid and topazolite); also in alkali-rich igneous rocks (melanite and schorlomite); and in metamorphosed limestones and contact zones (brown and green colors).

San Benito County, California: topazolite (N= 1.855-1.877, S.G. = 3.77-3.81), demantoid (N= 1.882, S.G. = 3.81), and unusual catseye material. Arizona: New Jersey; Pennsylvania.

Greenland; Norway; Sweden; Uganda; Ski LankaColorado: melanite.

Arkansas: schorlomite.

New Mexico: in metamorphic limestones and ore deposits.

USSR: fine demantoid from the Urals. Also some (small) brown andradite.

Zaire: brown and green andradite, also some demantoid.

Ala, Piedmont, Italy: dark apple green demantoid garnet; also topazolite (yellow).

Korea: andradite, some fine green with Cr.

Monte Somma, Vesuvius, and Trentino, Italy: melanite (black).

Its dispersion is much higher than any other garnet and even much higher than diamond. The dispersion is usually masked by dark body colors but small, light colored gems are dazzling!

The variety dematoid is colored green by chromium. This gem is always in high demand.

Andradites are known for their distinctive, horsetail inclusions. (See “Identifying Inclusions” in our Reference Library.) They are both an aid to the gemologist and a delight to collectors.

Andradite is seldom faceted, but brownish stones up to a few carats are known. Demantoid however, is a rare but well-known gem, and is probably the most valuable of all the garnets.

Smithsonian Institution (Washington, D.C): 10.4 (USSR); also 4.1, 3.4, and 2.3.

Private Collection: 18 (sold in New York Cityl; a California collector owns a huge topazolite (green color) that would yield faceted gems over 20 carats. This crystal weighs ~1 ounce.

USSR: many fine demantoids in museum collections.

OPTICS: N= 1.88-1.94; melanite:  1.89; demantoid: 1.881-1.888; schorlomite: 1.935; topazolite (yellow): 1.887.

INCLUSIONS: Demantoid is distinguished by so-called horsetail inclusions of byssolite (fibrous amphibole); these are diagnostic for this gem. These inclusions also occasionally produce catseye gems.