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The science of demantoid.
Why demantoid sparkles more than diamond, what gives it its colour, and what its inclusions tell you.
The mineral
Demantoid at a glance.
- Species
- Andradite garnet
- Formula
- Ca₃Fe₂(SiO₄)₃
- Refractive index
- ≈ 1.88 – 1.89
- Dispersion
- 0.057
- Hardness
- 6.5 – 7 Mohs
- Specific gravity
- ≈ 3.84
Demantoid is andradite’s green variety.
Calcium iron silicate.
Higher than most coloured gems.
Greater than diamond (0.044).
Wear with some care.
Denser than diamond (3.52).
Typical published values for andradite; individual stones vary slightly.
Dispersion compared
More fire than diamond.
Dispersion measures how strongly a gem splits white light into spectral colours — the flashes we call fire.
Demantoid’s dispersion is among the highest of any natural gem. In lighter, brighter stones it is especially visible; in deeper greens the body colour can mask part of it.
How fire is judged in our standardGo deeper
Learn more.
Questions
Common questions.
Why is demantoid so fiery?
Its dispersion — the splitting of white light into spectral colours — is about 0.057, higher than diamond’s 0.044. Colour and tone affect how visible that fire is.
Is demantoid durable enough for daily wear?
At 6.5–7 on the Mohs scale it is softer than sapphire or diamond. It suits pendants and earrings well; rings benefit from protective settings and careful wear.
Is demantoid treated?
Heat treatment is known to be used on some demantoid to modify colour. Ask for treatment disclosure and, where available, an independent report for any stone.
See the science in a stone.
Browse round demantoid by clarity — from eye-clean to classic horsetail.