Quick Facts
Formation & Origin
Demantoid is the green, chromium-bearing variety of andradite garnet. It forms in serpentinized ultramafic rocks where chromium-rich fluids react with iron and calcium in the host rock. The Ural Mountain specimens formed in serpentinite veins associated with the collision of tectonic plates that built the Urals.
Demantoid has the highest dispersion (fire) of any natural gemstone commonly used in jewelry: 0.057, exceeding even diamond (0.044). This means demantoid splits white light into spectral colors more effectively than diamond, producing exceptional rainbow flashes. The combination of vivid green body color with intense spectral fire creates one of the most visually dynamic gems in existence.
Russian demantoid is uniquely prized for containing 'horsetail' inclusions: curved, radiating fibers of chrysotile (a type of asbestos) that create a distinctive spray pattern within the stone. Paradoxically, these inclusions increase rather than decrease value, serving as a natural certificate of Russian origin.
Identification Guide
Demantoid is identified by its vivid green color, exceptional dispersion (visible fire even in daylight), and high refractive index (1.880-1.889) for a garnet. As an isometric mineral, it is singly refractive, which helps separate it from many green gems.
Distinguish from tsavorite (grossular garnet, lower RI, less fire), emerald (lower RI, typically included, hexagonal), chrome diopside (lower hardness, monoclinic, double refractive), and peridot (double refractive, different color tone). The combination of green color with exceptional fire is unique to demantoid.
Spotting Fakes
The main concern is disclosure of treatments and origin. Some demantoid is heat-treated to improve color. YAG (yttrium aluminum garnet) in green can imitate demantoid but lacks the correct RI and specific gravity. Lab reports from reputable gemological laboratories are recommended for expensive stones. Russian origin with horsetail inclusions commands the highest prices. Check for natural inclusions, as glass imitations will lack the characteristic internal features.
Cultural & Metaphysical Traditions
Presented as cultural traditions, not scientific evidence
Demantoid garnet was the favorite gemstone of Russian imperial jeweler Peter Carl Fabergé and was prominently featured in Romanov-era jewelry. Crystal practitioners associate it with confidence, abundance, and the ability to see beauty in all things. Its fire (dispersion) is seen as a symbol of inner light and creative spark.
Where It's Found
Original source, prized for horsetail inclusions
Clean stones, strong color, larger sizes
Growing source of demantoid
Some fine green andradite material
Price Guide
Good to Know
Scratch test: At hardness 6.5, Demantoid Garnet resists scratching from a knife but can be scratched by quartz. Best for pendants and earrings rather than rings.
Sources: Found in 4 notable locations worldwide, from Russia to Madagascar.
Heft test: Demantoid Garnet has a specific gravity of 3.82-3.85 - noticeably heavier than quartz. You'll feel the density when you pick it up.
Related Minerals
Green grossular garnet, different garnet species
Parent garnet species, demantoid is the green variety
Black variety of the same andradite species