Star Diopside

Key Differentiators

• 4-rayed star (not 6-rayed) — caused by two sets of magnetite/ilmenite needles perpendicular in (010) plane
• Black to dark greenish-black opaque body color
• Lower hardness than star corundum (5.0–6.0 vs 9.0) — easily scratched
• Strong magnetic response from magnetite needle inclusions
• India origin (Karnataka, Tamil Nadu) — essentially the only commercial source

Common Simulants

• Black Star Sapphire: Star sapphire is corundum (hardness 9, vs diopside 5–6). RI 1.762–1.778 vs diopside 1.664–1.721. Star sapphire typically shows 6 rays; star diopside shows 4 rays. Star sapphire is non-magnetic; star diopside shows weak magnetism from magnetite inclusions. SG 3.99–4.05 vs diopside 3.27–3.36.
• Black Star Spinel: Star spinel shows a 4-rayed star like diopside but is isotropic (SR, cubic) with single RI near 1.718. Diopside is biaxial (DR_B+) showing a birefringence spread of 0.030 on the refractometer. SG spinel 3.58–3.61 vs diopside 3.27–3.36.
• Glass with foil star: Glass is isotropic, much lower SG (typically 2.3–4.5), and the star is a surface reflection from a foil backing rather than internal asterism from needle inclusions. Under magnification the foil layer is visible at the base.

Commonly Confused With

Commonly confused with: Star Ruby, Star Sapphire.

Price Context

Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.

Measurement Guides

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