Sinhalite
Last updated: April 2026
Sinhalite is a rare borate mineral first described as a gem species in 1952 (originally misidentified as a brown peridot variety). It is still frequently misidentified as peridot, brown tourmaline, or zircon. The diagnostic triple absorption bands at 452, 475, and 493 nm in the spectroscope (Anderson 1990) are the definitive test. The high birefringence (0.038) produces strong facet doubling visible under 10× loupe.
Sinhalite has a specific gravity of 3.48 and a refractive index of 1.665–1.712, with a Mohs hardness of 6.5–7.0. It is biaxial −.
Physical & Optical Properties
Key Differentiators
- Diagnostic spectroscope absorption bands at 452, 475, and 493 nm — essentially unique to sinhalite
- Strong facet doubling visible under 10× loupe (birefringence 0.038)
- RI 1.665–1.712 with biaxial negative optic sign
- SG 3.47–3.50 — heavier than peridot (3.28–3.48)
- Distinct trichroism: pale brown / dark brown / greenish brown
Commonly Confused With
Commonly confused with: Peridot.
Price Context
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Related Comparisons
Measurement Guides
Identifying a sinhalite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Sinhalite 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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