Cat's Eye Chrysoberyl

Related: Chrysoberyl Varieties

AlexandriteChrysoberyl

Key Differentiators

• 'Milk and honey' effect: tilting the stone under a single point light reveals one half whitish ('milk') and one half gold/yellow ('honey') — unique to chrysoberyl among chatoyant gems
• High RI 1.746–1.755 — highest of any commercially significant chatoyant gem; definitive against all simulants
• High SG 3.70–3.78 — noticeably heavy for its size; all simulants are lighter
• Hardness 8.5 — no surface scratches from quartz or steel; harder than all simulants
• Single bright, sharp chatoyant band that moves smoothly as the stone is rotated under a point light
• No commercial synthetic exists — concern is simulant separation only

Natural vs. Synthetic

Synthetic cat's eye chrysoberyl is commercially available (Czochralski (pulled), Hydrothermal). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

• General Note: No commercial synthetic cat's eye chrysoberyl exists. All cat's eye chrysoberyl on the market is natural. Chatoyancy is caused by parallel growth tubes or silk inclusions aligned along the c-axis. Synthetic: No known synthetic. The primary concern is simulants — fiber-optic glass is the most common substitute. High RI (1.746–1.755) and SG (3.73) are definitive against all simulants.
• Refractometer: RI 1.746–1.755 (biaxial positive). This is the highest RI of any chatoyant gem encountered commercially. Synthetic: Fiber-optic glass: RI ~1.52 (isotropic). Apatite cat's eye: RI 1.634–1.638. Quartz cat's eye: RI 1.544–1.553. Scapolite cat's eye: RI 1.550–1.572. Tourmaline cat's eye: RI 1.624–1.644. All are conclusively lower.
• Specific Gravity: SG 3.70–3.78 (typical 3.73). Heavy for its size — will sink quickly in methylene iodide (SG 3.33). Synthetic: Fiber-optic glass SG ~2.6. Apatite SG 3.18. Quartz SG 2.65. Scapolite SG 2.65. All float or are noticeably lighter.

Common Simulants

• Fiber-optic glass (glass cat's eye): Most common simulant. Isotropic, RI ~1.52, SG ~2.6 (much lighter). Band often too uniform and narrow. Under darkfield: gas bubbles and curved flow lines. No milk-and-honey effect — the band stays the same color when stone is tilted. RI test separates cleanly.
• Apatite cat's eye: Similar honey-yellow color. RI 1.634–1.638 (lower). SG 3.18 (lighter). Hardness only 5 — scratched easily by a penknife. Uniaxial negative. Less pronounced milk-and-honey effect.
• Quartz cat's eye: Very common and inexpensive. RI 1.544–1.553 (much lower). SG 2.65 (noticeably lighter). Band typically less sharp. No milk-and-honey effect. Uniaxial positive.
• Tourmaline cat's eye: RI 1.624–1.644 (lower). SG 3.06 (lighter). Strong pleochroism visible when rotating stone. Band less sharp than chrysoberyl. Uniaxial negative with strong birefringence.
• Scapolite cat's eye: RI 1.550–1.572 (much lower). SG 2.65 (much lighter). Uniaxial negative. Rarely encountered; band quality typically inferior to chrysoberyl.

Treatments

• Dyeing (rare)
• Irradiation (rare — color modification)

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 Refractometer