Hessonite Garnet
Last updated: April 2026
Grossular is a calcium-aluminium garnet; the orange-brown variety is called Hessonite. Under 10× magnification, hessonite typically shows a distinctive "treacle effect" — a roiled, heat-shimmer appearance caused by diopside and apatite inclusions. This is diagnostic; no other orange stone shows this.
Hessonite Garnet has a specific gravity of 3.61 and a refractive index of 1.730–1.760, with a Mohs hardness of 7.0–7.5. It is singly refractive.
Physical & Optical Properties
Related: Garnet Varieties
Key Differentiators
- Treacly or roiled internal appearance
- Wide color range
- Tsavorite is the green variety
Common Simulants
- Citrine: Citrine is uniaxial negative DR; RI 1.544–1.553; SG 2.65; lower RI than hessonite (~1.742).
- Spessartite Garnet: Higher RI (1.810); stronger orange hue typically; isotropic like hessonite — difficult without refractometer.
- Glass: Gas bubbles, swirl marks under loupe; isotropic but SG varies widely; conchoidal fracture.
Commonly Confused With
Commonly confused with: Citrine, Spessartite Garnet, Glass, Padparadscha Sapphire.
Treatments
- Polymer / Resin Infusion (documented — GIA 2016)
- Heat Treatment (occasional — undetectable)
Price Context
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a hessonite garnet? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Hessonite Garnet is one of the 130 species in GemID’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
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