Demantoit

Demantoid is the green variety of garnet, belonging to the andradite subgroup of the garnet group. Its color ranges from bright emerald to grassy green, largely due to chromium and iron impurities within the crystal structure. The name demantoid comes from the German demant, meaning diamond, in reference to its notable brilliance and fire.

The stone was first described in the late 19th century from the Ural Mountains in Russia, where high‑quality stones earned a reputation for exceptional luster and dispersion. While the Urals remain the classic source, later deposits have been found in Namibia, Madagascar, and other locales, producing stones that can vary in tone and clarity.

Physically, demantoid garnet typically has a Mohs hardness of about 6.5 to 7, making it suitable for most jewelry with proper care. It exhibits a relatively high refractive index and a dispersion value around 0.057, contributing to its diamond‑like sparkle. The gemstone often occurs with characteristic inclusions in the Urals material, including slender chrysotile asbestos fibers that form "horsetail" patterns; these inclusions can aid origin identification but do not always affect durability.

In terms of use and value, demantoid is among the most prized green garnets due to its brightness and color saturation. Large, inclusion‑free crystals are rare, which can elevate price. It is cut for facets or cabochons in jewelry and is generally treated as a natural gemstone with no standard commercial treatments widely reported.