Demantoid Garnet
Last updated: April 2026
The green variety of andradite garnet, prized for its exceptional brilliance and fire. "Horsetail" inclusions (chrysotile fibers radiating from a chromite crystal) are diagnostic for Russian (Ural) demantoid but absent in Namibian material. Horsetails confirm andradite species but not the demantoid variety — color and RI confirmation are still required.
Physical & Optical Properties
RI Range1.880–1.895
SG Range3.82–3.88
SG Typical3.84
Hardness (Mohs)6.5–7
Crystal SystemCubic
Optic CharacterSR (Singly Refractive)
Dispersion0.057
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterRed
PleochroismNone
ColorsGreen, Yellow Orange
SpeciesGarnet
VarietyDemantoid
Related: Garnet Varieties
Key Differentiators
- Dispersion higher than diamond
- Horsetail inclusions
- Adamantine luster
Common Simulants
- Tsavorite Garnet: Tsavorite RI ~1.740 vs demantoid 1.888; demantoid has higher dispersion (fire) and characteristic horsetail inclusions.
- Peridot: Peridot is biaxial positive DR; characteristic doubling visible under loupe; RI 1.654–1.690; SG 3.34.
- Green zircon: Zircon shows strong doubling under loupe; very high SG (4.67); birefringence visible.
- Glass: Isotropic; gas bubbles or swirl marks under loupe; conchoidal fracture; SG much lower than demantoid (3.84).
Commonly Confused With
Commonly confused with: Tsavorite Garnet, Peridot, Zircon, Glass.
Treatments
- Heat Treatment (~800°F — undetectable)
Price Context
Natural — low ($/ct)$1,000
Natural — high ($/ct)$8,000
NotePer carat; fine Russian material with horsetail inclusions commands highest premiums
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a demantoid garnet? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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