Demantoid Garnet Identification Guide
Identify Demantoid Garnet by its vivid green color, diamond-like fire, isotropic optics, horsetail inclusions, and high density.
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What Demantoid Garnet Looks Like
Demantoid is the rare, brilliant green gem variety of andradite garnet, colored by chromium and iron. Its name means "diamond-like" because it has exceptional dispersion (fire) and a high refractive index, giving lively rainbow flashes. Color ranges from yellowish-green to deep emerald-green. It is typically seen as faceted gems or as dodecahedral/trapezohedral crystals.
- Color: yellowish-green to vivid green (chrome green in the best stones)
- Luster: adamantine to vitreous (notably bright)
- Transparency: transparent
- Habit: rhombic dodecahedra/trapezohedra; usually cut gems
Step-by-Step Field-ID Checklist
- Note the fire. Strong dispersion gives diamond-like rainbow sparkle unusual for a green stone.
- Look for horsetail inclusions. Russian demantoid often contains radiating golden byssolite "horsetail" inclusions, a near-unique diagnostic.
- Check optics. Garnet is singly refractive (isotropic); no doubling of facets (separates it from peridot and tourmaline).
- Hardness/heft. Mohs ~6.5-7, and it feels heavy (density ~3.8-3.9).
- Confirm color cause. Vivid chrome green plus high fire points to demantoid over other green garnets.
Key Diagnostic Tests
- Mohs hardness: 6.5-7 (softer than emerald/sapphire).
- Streak: white.
- Optical: isotropic (single refraction), high refractive index (~1.88), very high dispersion.
- Inclusions: radiating horsetail (byssolite) fibers in Russian material.
- Density: ~3.8-3.9 g/cm3 (heavy for its size).
Common Look-Alikes and How to Tell Them Apart
- Tsavorite (green grossular garnet): Also green garnet but lower dispersion (less fire) and a different inclusion suite; tsavorite lacks horsetails and has slightly lower density.
- Emerald: Doubly refractive, lower density (~2.7), much less fire, and typically more included with jardin; emerald is harder.
- Peridot: Yellow-green, doubly refractive with strong facet doubling, lower RI and density; demantoid is singly refractive.
- Green tourmaline: Doubly refractive, strongly pleochroic, lower density; demantoid is isotropic with high fire.
- Chrome diopside: Softer, doubly refractive, lower fire; lacks demantoid's brilliance and horsetails.
Where It Is Found
Classic demantoid comes from the Ural Mountains of Russia (famous for horsetail inclusions). Other notable sources include Namibia (Erongo/Green Dragon), Madagascar, Iran, and Italy.
Frequently asked questions
How can you tell if it's real Demantoid Garnet?
Real demantoid is a vivid green garnet with diamond-like fire, is singly refractive (no facet doubling), feels heavy (density ~3.8-3.9), and Russian stones often show radiating golden horsetail inclusions. High dispersion plus isotropic optics distinguish it from emerald, peridot, and tourmaline.
What does Demantoid Garnet look like?
It looks like a bright yellowish-green to emerald-green gem with exceptional rainbow fire and an adamantine luster, usually seen as faceted stones.
What are horsetail inclusions in Demantoid?
They are radiating sprays of fine golden byssolite (a fibrous amphibole) fibers that fan out like a horse's tail, characteristic of Russian Ural Mountain demantoid and often considered proof of natural origin and locality.
Demantoid vs tsavorite: what's the difference?
Both are green garnets, but demantoid is andradite with very high dispersion (fire) and can show horsetail inclusions, while tsavorite is grossular with lower dispersion, no horsetails, and slightly lower density.
Demantoid vs emerald: how do I tell them apart?
Demantoid is singly refractive with much more fire and a higher density (~3.8), while emerald is doubly refractive, lower density (~2.7), shows little fire, and is usually more included. A gemologist can confirm with a refractometer.