Demantoid
green · Garnet family
| Also known as | Garnet (Garnet family) |
|---|---|
| Colour | Green |
| Mohs hardness | 6.5–7.0 |
| Lustre | adamantine |
| Streak | White |
| Crystal system | cubic |
| Transparency | Can form with any diaphaneity, translucent is common |
| Cleavage | Indistinct |
| Fracture | conchoidal to uneven |
| Chemical formula | Ca 3 Fe 2 Si 3 O 12 |
| Specific gravity | 3.84 |
What is Demantoid?
Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.
How to identify Demantoid
- Lustre: adamantine.
- Hardness: Mohs 6.5–7.0 — about as hard as a steel knife.
- Streak: White.
- Habit: cubic crystal system.
Demantoid value
Demantoid is a fine gemstone priced per carat by quality — colour, clarity, cut, carat and origin — not by weight in grams. Typical market ranges:
| Quality | Price per carat |
|---|---|
| Commercial | $200–$1,500 / ct |
| Good | $600–$3,000 / ct |
| Fine | $3,000–$10,000 / ct |
| Top | $10,000–$50,000+ / ct |
Ranges cross-validated across two independent research passes against gemstone price guides, 2026-06 — sources: palagems.com, tsarinajewels.com. Colour saturation, clarity, cut and origin move the price enormously, and treatments or lab-grown stones sell for a fraction — so this is a guide, not an appraisal. Have anything valuable checked by a certified gemmologist. See the full crystal & gemstone value guide.
