Cat's Eye Beryl Identification Guide
Identify cat's eye beryl by its chatoyant light band over a beryl body, across colors, and distinguish it from chrysoberyl and quartz cat's eyes.
Read the full Cat's Eye Beryl encyclopedia entry →
What Cat's Eye Beryl Looks Like
Cat's eye beryl is any color variety of beryl (aquamarine, morganite, heliodor, emerald, goshenite) that shows chatoyancy — a moving band of light caused by fine parallel tube inclusions. The body color depends on which beryl variety it is.
- Color: ranges with variety — blue (aquamarine), pink (morganite), yellow (heliodor), green (emerald), colorless (goshenite).
- Luster: vitreous.
- Transparency: translucent to semi-transparent, slightly silky.
- Effect: a single soft light line crossing a cabochon dome.
Step-by-Step Field-ID Checklist
- Find the eye: one light source, rotate the cabochon — a clean band should glide across.
- Identify it as beryl: vitreous luster, hexagonal origin, hardness 7.5–8.
- Hardness test: scratches quartz and glass.
- Magnify the inclusions: parallel hollow tubes/fibers cause the chatoyancy.
- Note the variety by color to refine the trade name (e.g., cat's eye aquamarine vs cat's eye morganite).
Key Diagnostic Tests
- Mohs hardness: 7.5–8.
- Streak: white.
- Cleavage: indistinct basal; conchoidal fracture.
- Density: ~2.6–2.9 g/cm³.
- Refractive index: ~1.57–1.58.
- Effect: chatoyancy from parallel tubular inclusions.
Common Look-Alikes
- Chrysoberyl cat's eye (cymophane): the benchmark cat's eye; harder (8.5), denser (~3.7), sharper eye. Density and RI separate it clearly.
- Cat's eye quartz: softer (7), lower RI (~1.55), and a more diffuse band.
- Cat's eye tourmaline: stronger pleochroism and different RI; often deeper colors.
- Glass/fiber-optic imitation: "cat's eye glass" shows an unnaturally sharp, mechanical eye and a flat color, with gas bubbles under magnification.
Where Cat's Eye Beryl Is Found
Chatoyant beryl forms in granitic pegmatites with the right parallel growth structures. Principal sources are Brazil, Madagascar, and Sri Lanka, the same regions that yield gem beryl generally. Cat's eye examples are uncommon and always cut en cabochon.
Frequently asked questions
What is cat's eye beryl?
It is beryl of any color (aquamarine, morganite, heliodor, etc.) that displays chatoyancy — a single moving band of light caused by fine parallel tube inclusions — when cut as a cabochon.
How do you tell cat's eye beryl from chrysoberyl cat's eye?
Chrysoberyl cat's eye is harder (8.5 vs 7.5–8) and significantly denser (~3.7 vs ~2.7), with a sharper, brighter eye. Beryl's lower density and refractive index distinguish it.
How can you spot fake cat's eye glass?
Imitation fiber-optic glass shows an unnaturally crisp, mechanical eye, flat uniform color, and gas bubbles under magnification, whereas natural beryl shows fine tube inclusions and slight color variation.
Does the eye appear in faceted beryl?
No. Chatoyancy only shows on a domed cabochon cut across the parallel inclusions; faceting scatters the reflection and hides the effect.