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
Related: Garnet Varieties
Key Differentiators
- Deep red color
- High RI and SG
- Characteristic absorption spectrum
Common Simulants
- Ruby: Ruby is doubly refractive (uniaxial negative); shows strong red fluorescence under LW UV; Chelsea filter strongly red.
- Red Spinel: Also isotropic; distinguish by RI (spinel ~1.718 vs almandine ~1.790) and fluorescence pattern.
- Red tourmaline (rubellite): Uniaxial negative DR; dichroic (red/orange-red); RI 1.624–1.644; SG 3.06.
- Glass: Isotropic; gas bubbles and swirl marks under loupe; conchoidal fracture; SG much lower.
Commonly Confused With
Commonly confused with: Ruby, Spinel, Tourmaline, Glass, Pyrope Garnet, Rhodolite Garnet.
Treatments
- Fracture Filling (glass/resin)
Price Context
Natural — low ($/ct)$10
Natural — high ($/ct)$150
NotePer carat; common gem; commercial to fine quality
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying an almandine garnet? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Almandine 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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