Cat's Eye Obsidian Identification Guide

What Cat's Eye Obsidian Looks Like

Cat's Eye Obsidian is ordinary volcanic glass (obsidian) that shows a soft, mobile band of reflected light, or chatoyancy, when cut as a cabochon. The body color is usually black, smoky brown, gray-green, or olive, and the eye appears as a single silvery, greenish, or golden stripe that glides across the dome as you rotate the stone under a single light. The luster is bright and glassy (vitreous), and rough pieces are translucent only on thin edges.

Key Visual Traits

• Glassy, often slightly resinous surface luster
• Conchoidal (shell-like, curved) fracture with razor edges on broken pieces
• A soft "moving" light band rather than discrete sparkles
• Chatoyancy caused by aligned microscopic gas bubbles or fibrous mineral inclusions

Step-by-Step Field-ID Checklist

1. Roll it under a point light. A genuine cat's eye band sweeps smoothly across a polished dome. No band means it is plain obsidian.
2. Check the break. Hunt for the classic curved, glassy conchoidal fracture with no cleavage planes.
3. Test hardness. Obsidian sits at about 5 to 5.5 on the Mohs scale; a steel knife will barely scratch it, and quartz will scratch it.
4. Check the streak. It leaves a white to pale gray streak on an unglazed tile.
5. Feel the weight. Specific gravity is low, roughly 2.35 to 2.6, so it feels light for its size, lighter than equivalent agate.
6. Look for warmth. Glass warms quickly in the hand, unlike denser quartz cat's eyes.

Diagnostic Tests

• Hardness: 5 to 5.5 (softer than quartz at 7).
• Fracture: Conchoidal, no cleavage.
• Streak: White.
• Density: Low (about 2.4), feels light.
• Magnetism/acid: Non-magnetic; inert to dilute acid.
• Transparency: Translucent thin edges, opaque body.

Common Look-Alikes and How to Tell Them Apart

• Cat's Eye Quartz / Tiger's Eye: Harder (Mohs 7, will not be scratched by a knife) and denser. Tiger's eye shows golden fibrous bands with a silky, not glassy, luster.
• Cat's Eye Chrysoberyl: Far harder (8.5), heavier, and shows a sharp, bright "milk and honey" eye; obsidian's eye is softer and more diffuse.
• Manufactured fiber-optic "cat's eye" glass (cat's eye simulant): Shows an unnaturally crisp, perfectly straight eye and often a grid of parallel lines under magnification; obsidian's eye is more natural and slightly hazy.
• Plain obsidian: No light band at all.
• Black tourmaline or jet: Tourmaline is harder with striated crystals; jet is much lighter, warm, and can smell of coal when hot-point tested.

Where It Is Typically Found

Obsidian forms where silica-rich (rhyolitic) lava cools too fast to crystallize, so cat's eye material comes from young volcanic regions: Mexico, the western United States (Oregon, California, Arizona, Nevada), Armenia, and Indonesia. Note that most cat's eye obsidian on the market is cut from sheen obsidian, where bubble alignment produces the effect; gem-quality eyes are selected and oriented during cutting.

Collector and Field Notes

When buying or sorting rough, remember the eye only appears after the dome is cut and oriented across the bubble or fiber alignment, so unoriented rough may hide its potential. Cabochons should be cut with the band centered for the best effect. Because the chatoyancy is a structural effect rather than a color, it survives in low light and is best judged by slowly rocking the stone under a single bare bulb or the sun. Avoid thermal shock and tumbling against harder gems, since obsidian chips and develops edge fractures easily. A loupe will often reveal the fine parallel bubble trains responsible for the eye, a quick confirmation that the material is natural volcanic glass.