Andradite
Andradite is nesosilicate (garnet group), Ca₃Fe₂(SiO₄)₃. In the hand, it rates 6.5 to 7 on the Mohs scale, and it runs green (demantoid) and yellow-green. Calcium-iron garnet spanning brilliant green demantoid to glossy black melanite, always in rounded 12- or 24-faced crystals with near-diamond luster.
The geology.
Andradite carries the formula Ca₃Fe₂(SiO₄)₃. It belongs to the isometric system. Catalogues list it as nesosilicate (garnet group).
It sits at 6.5 to 7 on the Mohs scale. The surface reads adamantine to resinous. Light behaviour is transparent to opaque. Specific gravity runs 3.8 to 3.9. The streak is white. It breaks with no cleavage; conchoidal fracture.
Calcium-iron garnet spanning brilliant green demantoid to glossy black melanite, always in rounded 12- or 24-faced crystals with near-diamond luster.
It reaches buyers as dodecahedral crystals, druzy crusts, faceted demantoid or black melanite clusters.
The origins.
Skarns and serpentinites; demantoid from Russia (Urals), Namibia, Madagascar; melanite from Mali, Mexico, San Benito (USA).
On value, the database notes: melanite affordable; fine demantoid is among the priciest garnets.
Traditional associations.
In energy work traditions, associated with vitality and dynamic creative energy.
We keep this section because people ask. It sits below the geology on purpose, and none of it describes something the stone does.
Spotting the real thing.
Calcium-iron garnet spanning brilliant green demantoid to glossy black melanite, always in rounded 12- or 24-faced crystals with near-diamond luster.
Green glass and chrome diopside are sold as demantoid; horsetail inclusions are a badge of genuine Ural stones.
| Looks like | How to tell them apart |
|---|---|
| Black tourmaline | Schorl forms striated prisms; melanite forms equant faceted balls |
| Peridot | Demantoid has higher fire and forms dodecahedra, not granular masses |
| Green glass | Bubbles, light weight, molded shapes |
At-home tests.
Before anyone talks you into a lab report, these are the checks worth doing yourself on andradite.
| Test | What you should see |
|---|---|
| By eye | Dodecahedral form and brilliant luster |
| By eye | Heavy in hand (SG ~3.85) |
| Under a loupe | Demantoid often shows golden 'horsetail' fiber inclusions under a loupe |
Destructive tests belong to a gemologist, not a kitchen table. If a piece matters to you, pay for an appraisal before you take a file to it.
Care & handling.
At 6.5 to 7 on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with no cleavage; conchoidal fracture, which is worth knowing before you set it or drop it.
Clean it by hand, dry it properly, and keep it away from ultrasonic cleaners and hot steam.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Ca₃Fe₂(SiO₄)₃. Crystal system: Isometric. Specific gravity: 3.8 to 3.9. Streak: White. Cleavage and fracture: No cleavage; conchoidal fracture.
How it reaches the market
Skarns and serpentinites; demantoid from Russia (Urals), Namibia, Madagascar; melanite from Mali, Mexico, San Benito (USA).
What it gets confused with
Black tourmaline: Schorl forms striated prisms; melanite forms equant faceted balls. Peridot: Demantoid has higher fire and forms dodecahedra, not granular masses. Green glass: Bubbles, light weight, molded shapes.
What it is worth
Melanite affordable; fine demantoid is among the priciest garnets.
Where buyers get caught
Green glass and chrome diopside are sold as demantoid; horsetail inclusions are a badge of genuine Ural stones.
One more thing
Demantoid's dispersion, its rainbow fire, exceeds diamond's, which is exactly what its name means in old Dutch.
An education-first guide.
We do not stock andradite. Writing it up regardless is the point of a reference library.
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