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Almandine Garnet

Last updated: April 2026

The most common garnet, known for its deep red to purplish-red colors.

Almandine Garnet has a specific gravity of 4.05 and a refractive index of 1.770–1.830, with a Mohs hardness of 7.0–7.5. It is singly refractive.

Physical & Optical Properties

RI Range1.770–1.830
SG Range3.93–4.30
SG Typical4.05
Hardness (Mohs)7–7.5
Crystal SystemCubic
Optic CharacterSR (Singly Refractive)
Dispersion0.024
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsRed Pink, Purple, Brown
SpeciesGarnet
VarietyAlmandine
Red PinkPurpleBrown

Measured with a polariscope, a refractometer, a hydrostatic balance, a Chelsea filter, a UV torch, a loupe, a darkfield loupe and a spectroscope — step-by-step for each.

Through the refractometer

Almandine Garnet varies 1.770 – 1.830 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 REFRACTIVE INDEX DORotate the stone through a full 360°, watching the boundary. SEEOne boundary that does not move as you rotate. Where it sitsis not fixed for this species, though: published at 1.770 –1.830, and the stone drawn here reads 1.800 — the dashedmark is the one end of that range this scale can show. MEANSSingly refractive — a stationary single edge through thewhole rotation says so. The value itself is only anarrowing: this species spans 6 printed divisions, so areading places your stone inside the range rather thannaming it. The top of that range is past the 1.81 ceiling,so some stones of this species give no reading at all. Computed from gems.json — edge positions are arithmetic, not drawn. RI increases upward; the field above the boundary is the dark one.

Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.

Color-Change GarnetDemantoid GarnetHessonite GarnetPyrope GarnetRhodolite GarnetSpessartite GarnetStar GarnetTsavorite Garnet

Key Differentiators

Common Simulants

Commonly Confused With

Commonly confused with: Ruby, Spinel, Tourmaline, Glass, Pyrope Garnet, Rhodolite Garnet.

Treatments

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing

Identifying an almandine garnet? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.

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Studying for the GIA, FGA, or FEEG practical? Almandine Garnet is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.

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