Demantoid
AndraditeJewelryWiki Editorial·2 sources·Reviewed 2026-08-04
The rarest and most valuable garnet — a green andradite with more fire than diamond. Its dispersion (0.057) exceeds diamond’s (0.044), which is where the name comes from: "diamond-like". Russian demantoid often contains radiating "horsetail" inclusions, and unusually for a gem, those inclusions RAISE the value because they prove the origin.
Properties
| Property | Value | Authority |
|---|---|---|
| Mohs hardness | 6½–7 [1] | — |
| Specific gravity | 3.8–3.9 [1] | — |
| Chemical formula | Not published. Andradite’s formula places a charge superscript and a subscript at the same position in the source, and this site does not guess at which digit belongs to which — the same reason almandine and spessartine are blank. [2] | — |
| Crystal system | Cubic [1] | — |
| Common treatments | Garnets are among the few coloured stones sold essentially untreated. Horsetail inclusions should be looked for, not avoided. [2] | — |
| Suitability for daily wear | Good, and no cleavage — but it is a stone usually bought as a collector’s piece rather than an everyday ring. [2] | — |
Sources
- Handbook of Mineralogy — Mineral Data Publishing / Mineralogical Society of America (Handbook of Mineralogy, Mineral Data Publishing)
- International Gem Society — gemstone articles — International Gem Society (IGS, gemstone information articles (gemsociety.org))