Demantoid is a member of the garnet group of minerals. It is a green gemstone variety of andradite, which is a garnet rich in calcium and iron. The chemical formula is Ca3Fe2(SiO4)3. The chromium substitution is the cause of the demantoid’s green color. Presence of Ferric iron is the cause of the yellow color in the stone.

Demantoid has two misnomers such as livine, and Uralian emerald. Since Demantoid is the green variety of andradite garnet, it is always primarily green in color. Its color shade ranges from a very strong yellowish green to the color of a fine emerald. Some stones have a brownish cast, which is due to the presence of iron.

The dispersion of a demantoid is unusually high, and this exhibits itself as a visible “fire” of rainbow-colored flashes of light. This effect becomes less noticeable due to the green color of the stone.

Demantoids are generally very small and the polished stones may weigh under 1 carat or 200 mg. Bigger stones over 2 carats or 400 mg are rare. Stones over 3 carats or 600 mg are very rare.

Stones with more intense green coloration are generally highly valued. But it is the lighter stone of yellowish green which displays substantially more fire. The choice of stone color or the fire emitted by it is entire personal.

Russian demantoid often contain inclusions of a type of asbestos. These inclusions are feathery golden threads which tend to curve and resemble the tail of a horse. Hence they are referred to as ‘horsetail inclusions’. The presence of such inclusions indicate a natural and genuine demantoid. Such gemstones become more valuable because of their horsetail inclusions.

The micro structure of demantoid is affected by the presence of the ‘horsetails’. The ‘horsetail’ typically originates at the center of the nodule and the fibers branch out and radiate towards the surface. The demantoid free from the horsetail inclusions displays flat crystal faces.