Rock IdentifierTiger's Eye
Key takeaways
- Tiger's eye is fibrous quartz that shows chatoyancy — a moving 'cat's-eye' sheen.
- It forms when quartz replaces fibrous crocidolite, preserving the fibers.
- Dyed versions (red, blue 'hawk's eye') and glass imitations exist.
What it is
Tiger's eye is a variety of quartz that forms when silica replaces the fibrous mineral crocidolite, preserving its parallel fibers. Light reflecting off those aligned fibers produces chatoyancy — a silky band that glides across the surface as you tilt the stone. The classic color is golden brown; the blue-grey version is called hawk's eye.
How to recognize it
The moving silky sheen is the signature — rotate a polished piece and watch the bright band sweep across it. It has full quartz hardness (7, scratches glass) and a warm brown-gold color with fine parallel striping. That combination of chatoyancy plus quartz hardness separates it from softer, duller look-alikes.
Treatments & fakes
Natural tiger's eye is inexpensive, but it's often heat-treated or dyed into reds and other unnatural colors, which are legitimate when disclosed. Fiber-optic glass 'cat's-eye' is a common imitation — it shows a too-perfect, sharp single line of light and is often unnaturally vivid (bright green, pink), whereas real tiger's eye has a softer, broader sheen and earthy tones.
