Enstatite
Last updated: April 2026
Chrome enstatite is a chromium-bearing orthorhombic pyroxene producing rich green color, found primarily in Madagascar, Myanmar, and India; it is a collector's gemstone due to its low hardness, perfect cleavage, and limited availability in faceted form.
Enstatite has a specific gravity of 3.27 and a refractive index of 1.663–1.673, with a Mohs hardness of 5.0–5.5. It is biaxial +.
Physical & Optical Properties
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
Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.
Key Differentiators
- Chelsea filter red reaction — chromium-bearing; shared with chrome diopside but different RI/SG
- Low hardness 5–5.5 (scratched by quartz H 7 and feldspar H 6); practical cutting challenges
- Perfect cleavage in two prismatic directions at nearly 90° — risk of cleavage during cutting and wear
- Biaxial positive; RI 1.663–1.673 range is characteristic vs. chrome diopside (RI 1.664–1.730, biaxial negative)
- Strong trichroism (green / yellow-green / brown-green) distinguishes from isotropic green garnets
Common Simulants
- Chrome Diopside: Chrome diopside: biaxial negative (B-), RI 1.664–1.730 (higher upper end), SG 3.22–3.38; Chelsea red from Cr; similar green color. Optic sign and upper RI limit separate from enstatite (B+, RI max 1.673).
- Chrome Tourmaline: Tourmaline: uniaxial negative (DR), RI 1.624–1.644 (lower), strong dichroism, Chelsea red from Cr; hardness 7–7.5 (harder than enstatite); SG 3.00–3.20.
- Green Glass: Isotropic (SR), no pleochroism, gas bubbles or swirl marks under loupe; variable RI and SG depending on formulation; no cleavage planes.
Measurement Guides
Identifying an enstatite? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.
Try Loupewise Free →Studying for the GIA, FGA, or FEEG practical? Enstatite is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
Practice exams →