Demantoid is a garnet gemstone variety with an emerald-green color and mesmerizing, diamond-like sparkle. This type of garnet originates from Russia, sometimes dubbed the “Czar of garnets.” It’s known for being the most brilliant and currently most valuable garnet variety.

Are demantoids rare? Very rare — one of the rarest varieties of garnet, in fact! You probably know red garnets the best, as green is one of the rarest but also very desirable garnet colors. Even further, demantoid is one of the rarest colored gemstones, too!

Demantoid is a brilliant green semi-precious gemstone in the andradite garnet species. The only other green garnets are uvarovite, tsavorite, sometimes Mali garnet, and of course, demantoid.

Because it resembles peridot, other names used for demantoid include olivine, Uralian emerald, Ural chrysolite, Siberian chrysolite, and Bobrovsk emerald. However, these are all incorrect and against regulations set by the Federal Trade Commission (FTC).

As a garnet, demantoid serves as a birthstone for January, as well as a Capricorn or Aquarius zodiac stone. Additionally, green garnets traditionally commemorate the 25th wedding anniversary!

Demantoid Specifications & Characteristics

Demantoid is an andradite, the iron- and calcium-rich garnet species — formula Ca3Fe2(SiO4)3 — in the larger ugrandite garnet group. Other andradite garnets are topazolite, melanite, and rainbow andradite, but demantoid is the most valuable and widely known andradite variety.

The easiest way to identify demantoids is by the presence of horsetail inclusions (discussed more in-depth in the Clarity section). Not every demantoid has these inclusions, but demantoid is the only green gemstone that has them. Outside of demantoid, they’ve only been found in brown andradite as of 2018.

With a Mohs scale ranking of 6.5 to 7, demantoid’s hardness is the only trait that puts it slightly below other garnets.

On the other hand, demantoid beats other garnets with its diamond-like luster and high dispersion (a.k.a. “fire” or colorful sparkle). The dispersion (0.057) is even higher than that of diamond at 0.044!

Here are all of the demantoid garnet properties:

• Mineral family: Andradite Garnet

• Mohs hardness: 6.5-7

• Color: Yellow-green, emerald-green, or deep green, sometimes brownish tint

• Crystal structure: Isometric/Cubic

• Luster: Adamantine

• Transparency: Transparent

• Refractive index: 1.880-1.888

• Density: 3.81-3.89

• Cleavage: None

• Fracture: Conchoidal

• Streak: White

• Luminescence: None

• Optical effects: Rarely chatoyancy

• TREATMENT NONE

• COLOR GREEN

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