Grossular Garnet
Grossular garnet ranges from colorless (leuco-grossular) to delicate mint green (Merelani mint, Tanzania); the mint variety owes its subtle color to trace vanadium and chromium and is softer in tone than the vivid tsavorite variety of the same species.
Physical & Optical Properties
RI Range1.734–1.759
SG Range3.57–3.73
SG Typical3.61
Hardness (Mohs)6.5–7.5
Crystal SystemCubic
Optic CharacterSR (Singly Refractive)
Dispersion0.028
Fluorescence LWWeak orange
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsColorless, Green
SpeciesGarnet (grossular — calcium aluminum silicate)
VarietyLeuco-grossular / Merelani Mint Grossular
Key Differentiators
- Colorless (leuco) to delicate mint green — paler, softer green than tsavorite (which is rich saturated green)
- Isotropic SR garnet — no birefringence, no pleochroism; distinguishes from peridot (birefringent) and tourmaline (birefringent)
- Hessonite variety: diagnostic roiled 'heat-wave' / treacle inclusions under loupe — a reliable indicator
- RI 1.734–1.759 — lower than tsavorite (1.740–1.742 typical) and well below andradite/demantoid
- Chelsea filter inert in colorless and mint green (Cr-bearing tsavorite shows red on Chelsea)
Common Simulants
- White Sapphire: Uniaxial DR, birefringent (0.008), RI 1.762–1.778, SG 3.99–4.01. Much higher SG and birefringent — easy separation from isotropic grossular.
- White Topaz: Biaxial DR, RI 1.619–1.627, birefringence 0.008–0.010, SG 3.49–3.57. Lower RI and birefringent — clearly separable from grossular on refractometer.
- Green Tourmaline (mint / Paraiba-type): Uniaxial DR, birefringent (0.014–0.021), RI 1.614–1.666. Birefringence visible under loupe. Lower RI and birefringent vs. isotropic grossular.
- Prehnite (mint green): Biaxial DR, RI 1.616–1.649, SG 2.80–2.95. Much lower RI and SG than grossular; commonly shows botryoidal inclusions.
- Cubic Zirconia (colorless): Isotropic SR, RI over refractometer limit (~2.15), SG 5.6–5.9 — far denser than grossular. Easy separation by SG.
Treatments
- Fracture Filling (very rare)
Price Context
Natural — low ($/ct)$20
Natural — high ($/ct)$600
NoteColorless leuco-grossular: $20–100/ct; Merelani mint grossular (Tanzania): $100–600/ct for fine mint green stones; rarity and demand for Merelani mint is increasing
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
About Grossular Garnet
Grossular garnet ranges from colorless (leuco-grossular) to delicate mint green (Merelani mint, Tanzania); the mint variety owes its subtle color to trace vanadium and chromium and is softer in tone than the vivid tsavorite variety of the same species.
Identifying a grossular garnet? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →