---
title: "Demantoid: meaning in gemology"
description: "Demantoid is the green variety of andradite, a garnet species of calcium, iron and silicon. Chromium causes its color."
url: https://digitalgemology.com/learn/glossary/demantoid
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Colored gemstones

# Demantoid

Also called demantoid garnet, andradite, green andradite

Demantoid is the green variety of andradite, a garnet species of calcium, iron and silicon. Chromium causes its color.

## Properties

**Gemological properties of demantoid**

| Refractive index | 1.881 to 1.888 (demantoid); andradite 1.855 to 1.95 |
| --- | --- |
| Birefringence | None (singly refractive) |
| Optic character | Singly refractive |
| Dispersion | 0.057 |
| Specific gravity | 3.82 to 3.88 (demantoid); andradite 3.70 to 4.10 |
| Hardness (Mohs) | 6.5 to 7 |
| Crystal system | Cubic |
| Pleochroism | None |
| Absorption spectrum | Strong band, with cutoff at the violet end, 443 nm; doublet, sometimes visible in demantoid, 701 nm (Cr); sharp line, 693 nm (Cr); band in the orange, 640 nm (Cr); band in the orange, 622 nm (Cr) |

Published values. They change a little from stone to stone. Our tools do not model demantoid yet. Sources: [International Gem Society](https://www.gemsociety.org/article/andradite-garnet/) · [GIA](https://www.gia.edu/garnet) · [Gemdat](https://www.gemdat.org/gem-223.html)

## In more detail

Andradite is softer than grossular, but it has a higher refractive index and more dispersion. Cutters often use exact proportions to show demantoid's fire. Some demantoids have horsetail inclusions, radiating bundles of mineral fibers, which can raise their value. A horsetail does not prove Russian origin, because demantoids from Iran and Italy can have them too.

## Related terms

- [Garnet](https://digitalgemology.com/learn/glossary/garnet): Garnet is a group of closely related mineral species. They share the same crystal structure but differ in chemical composition.
- [Grossular](https://digitalgemology.com/learn/glossary/grossular): Grossular is a garnet species made of calcium, aluminum and silicon. It has perhaps the widest color range of any garnet species.
- [Dispersion](https://digitalgemology.com/learn/glossary/dispersion): Dispersion is how differently a stone bends red and violet light. Gemologists give it as the index difference between the B line (686.7 nm) and the G line (430.8 nm).
- [Fire](https://digitalgemology.com/learn/glossary/fire): Fire is the flashes of spectral color that a cut stone sends out. In our census, fire is the share of returned light whose colors leave more than 0.6° apart.
- [Inclusion](https://digitalgemology.com/learn/glossary/inclusion): An inclusion is a clarity characteristic inside a diamond, or one that reaches the surface from inside.

[All 369 terms](https://digitalgemology.com/learn/glossary)