Color-Change Garnet

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Physical & Optical Properties

RI Range1.740–1.765

SG Range3.65–3.80

SG Typical3.72

Hardness (Mohs)7–7.5

Crystal SystemCubic

Optic CharacterSR (Singly Refractive)

Dispersion0.026

Fluorescence LWInert

Fluorescence SWInert

Chelsea FilterVariable

PleochroismNone

ColorsColor Change, Blue Violet, Green, Red Pink, Purple

SpeciesGarnet

VarietyPyrope-Spessartite

Key Differentiators

Singly refractive (isotropic) — stays dark under polariscope; alexandrite is doubly refractive and blinks
No pleochroism — alexandrite shows strong pleochroism in three directions
High RI (1.740–1.765) and SG (3.65–3.80) — overlaps alexandrite but polariscope test is definitive
Color change from blue-green/grey-blue (daylight) to purple-red (incandescent)

Natural vs. Synthetic

Synthetic color-change garnet is commercially available (Flame fusion / Verneuil (synthetic corundum simulant only; no true synthetic garnet)). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

General Note: No synthetic color-change garnet. Confirm garnet: SR (isotropic, stays dark between crossed polars or shows anomalous DR), high RI 1.740–1.765, SG 3.65–3.80. Synthetic: Synthetic color-change corundum (lab sapphire): uniaxial negative DR, RI 1.762–1.778, SG 3.99 — doubly refractive, very different SG from garnet. Synthetic alexandrite: biaxial positive DR, RI 1.746–1.755, SG 3.70–3.78 — blinks under polariscope, shows pleochroism.

GemID Pro includes a two-phase natural vs. synthetic testing protocol for Color-Change Garnet.

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Common Simulants

Alexandrite: Alexandrite: DOUBLY REFRACTIVE — blinks distinctly between crossed polars; shows strong pleochroism in three directions (red, orange, green). RI 1.746–1.755; SG 3.70–3.78; biaxial positive. Color-change garnet is SR (no blink, no pleochroism).
Synthetic Color-Change Corundum: Uniaxial negative DR; RI 1.762–1.778; SG 3.99 — much higher SG than garnet. Blinks under polariscope. Shows pleochroism.

Commonly Confused With

Commonly confused with: Alexandrite.

Price Context

Natural — low ($/ct)$300

Natural — high ($/ct)$8,000

NotePer carat; strong blue-green to vivid purple-red change commands high premiums; Madagascar and Tanzania material most prized; size rarity above 2 ct

Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.

Related Comparisons

Measurement Guides

Identifying a color-change garnet? GemID walks through these tests in order — RI, SG, fluorescence, and more.

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