Star Ruby

← Back to Reference Database RI Chart SG Chart Fluorescence Hardness

Physical & Optical Properties

RI Range1.762–1.770

SG Range3.97–4.05

SG Typical4.00

Hardness (Mohs)9

Crystal SystemTrigonal

Optic CharacterDR Uniaxial (−)

Birefringence0.008

Dispersion0.018

Fluorescence LWVariable

Fluorescence SWVariable

Chelsea FilterRed

PleochroismStrong Dichroic

ColorsRed Pink

SpeciesCorundum

Key Differentiators

6-rayed star under point light source (asterism)
Caused by intersecting rutile silk needles at 60°/120°
Hardness 9 — not scratched by anything except other corundum/diamond
Strong red LW fluorescence typical

Natural vs. Synthetic

Synthetic star ruby is commercially available (Flame fusion / Linde process (most common synthetic star ruby)). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

GemID Pro includes a two-phase natural vs. synthetic testing protocol for Star Ruby.

Start Free Trial

Common Simulants

Star spinel: Isotropic (SR); star has 4 rays vs ruby's 6; different fluorescence; check with refractometer.
Star garnet: Isotropic SR; 4-rayed star; inert under UV; RI 1.720–1.760 range; no Chelsea filter reaction.
Glass with foil star: Isotropic; star is a surface reflection from foil backing, not internal asterism; visible as flat reflective layer under magnification.

Commonly Confused With

Commonly confused with: Spinel, garnet, glass, Star Diopside, Star Garnet.

Treatments

Low-Temperature Heat Treatment (< 1200°C)
High-Temperature Heat Treatment (> 1400°C)
Lead Glass Fracture Filling
Surface Coating (clarity or star enhancement)
Beryllium Diffusion (color alteration — laboratory detection only)

Price Context

Natural — low ($/ct)$100

Natural — high ($/ct)$10,000

NotePer carat; fine translucent Burmese star rubies with vivid color and sharp 6-ray star can reach $3,000–$10,000/ct; most commercial star rubies are opaque and worth $100–$500/ct

Synthetic — low ($/ct)$5

Synthetic — high ($/ct)$40

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

About Star Ruby

Star ruby displays a 6-rayed star from three sets of rutile silk inclusions at 60° intervals (asterism), visible under a single point light above a well-cut cabochon. Synthetic star rubies (Linde/Verneuil process) show a very sharp centered star and are common in vintage jewelry from the 1950s–1970s. Heat treatment dissolves silk needles, so fine natural star rubies are typically unheated.

Identifying a star ruby? GemID walks through these tests in order — RI, SG, fluorescence, and more.

Try GemID Free →