Cat's Eye Obsidian

Cat's Eye Obsidian is a sheen variety of obsidian, natural volcanic glass, that shows chatoyancy: a bright, moving band of light across the surface resembling a cat's slit pupil. The effect comes from countless aligned microscopic inclusions (tiny gas bubbles or crystallites) that reflect light into a single concentrated line.

The stone must be cut as a domed cabochon with the inclusion layer oriented correctly for the 'eye' to appear and glide as the stone is tilted. The body color is usually black to dark grey.

It is closely related to silver-sheen and gold-sheen obsidian; cat's eye obsidian simply concentrates that sheen into a band rather than a broad glow.

Cat's Eye Obsidian forms like all obsidian, from silica-rich lava quenched into glass at a volcano's surface. As the lava cooled, vast numbers of microscopic gas bubbles or incipient crystallites became trapped and aligned along flow planes.

When a cabochon is cut so the dome's base is parallel to that aligned layer, light reflecting off the many parallel inclusions converges into a single bright line, producing chatoyancy. The orientation of the cut, not a separate mineral, creates the eye.

This sheen-bearing obsidian comes from the same flows that yield silver- and gold-sheen material, notably in Mexico and the western United States.

Look for a polished black or grey obsidian cabochon with a single sharp band of silvery light that moves across the dome as you tilt it under a point light source. Hardness is 5-5.5, luster vitreous, fracture conchoidal, streak white.

The eye is a reflection effect, so it only appears in properly cut, domed pieces, not in rough.

Distinguish it from true chrysoberyl cat's eye, which is far harder (8.5) and a crystalline gemstone, and from cat's eye quartz (harder at 7, formed by fibrous inclusions). Obsidian's softness, glassy fracture, and a single broad reflective band confirm it.

Cat's Eye Obsidian is cut almost exclusively as domed cabochons to display chatoyancy, then set into pendants, rings, and earrings. Cutters must orient the rough precisely to center the eye. It polishes brilliantly but, as glass, can chip and benefits from protective settings.

Generic obsidian has been used since prehistory for sharp tools and mirrors.

Metaphysically, cat's eye obsidian is associated with protection and focused insight, the 'eye' said to deflect negativity; these are traditional beliefs rather than scientific facts.