Indicolite
Last updated: April 2026
Blue to greenish-blue elbaite tourmaline. Separated from blue sapphire by much lower RI and strong birefringence producing facet doubling. Differs from aquamarine by stronger dichroism, higher SG, and facet doubling. Generally inert to LW UV. No commercial synthetic.
Indicolite has a specific gravity of 3.06 and a refractive index of 1.624–1.644, with a Mohs hardness of 7.0–7.5. It is uniaxial −.
Physical & Optical Properties
Related: Tourmaline Varieties
Key Differentiators
- Strong dichroism — dark blue vs. light blue/colorless when rotated
- Blue with greenish modifier typical; both ends of dichroscope visible
- Birefringent — facet doubling visible under 10×
- Lower RI than sapphire (1.762) or aquamarine (1.577–1.590)
Common Simulants
- Blue sapphire: Sapphire: uniaxial negative; RI 1.762–1.778; SG 4.00; dichroic; much higher RI; harder (9 Mohs); no facet doubling.
- Aquamarine: Aquamarine: uniaxial negative; RI 1.577–1.590; SG 2.72; weaker pleochroism; lower RI; no facet doubling visible at 10×.
- Iolite: Iolite: biaxial negative; RI 1.54–1.56; SG 2.58–2.66; lower RI; trichroic (blue/yellow-grey/colorless), not dichroic.
- Blue Glass: Isotropic; no dichroism; gas bubbles under loupe; conchoidal fracture; no facet doubling.
Commonly Confused With
Commonly confused with: Sapphire, Aquamarine, Glass.
Treatments
- Heat Treatment (to lighten dark blue or remove brownish modifiers)
- Irradiation (to deepen or alter blue color)
Price Context
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying an indicolite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Indicolite 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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