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.

About Cat's Eye Chrysoberyl

Cat's eye chrysoberyl (cymophane) chatoyancy is caused by parallel growth tubes or rutile needles aligned along the crystallographic c-axis. The 'milk and honey' effect — one side appearing white, the other gold under a point light — is a field diagnostic rarely seen in other chatoyant gems. Always cut as a cabochon. Sources include Sri Lanka, Brazil, India, Zimbabwe, and Russia. No commercial synthetic exists; separation from simulants uses RI.