Tumbled tiger’s-eye

Mohs hardness 6.5–7; golden-brown chatoyant bands, vitreous-to silky luster, opaque, microcrystalline quartz, no obvious cleavage; specific gravity about 2.6–2.7.

A fibrous quartz replacement formed when crocidolite asbestos fibers were silicified and later oxidized to iron-rich brown-gold colors, typically in Precambrian metamorphic rocks. Major deposits occur in South Africa, Western Australia, and Namibia.

Commonly tumbled for collections and carved into cabochons, beads, and ornamental objects; relatively inexpensive jewelry stone.

Its shifting “cat’s-eye” sheen is called chatoyancy and is strongest when the stone is polished parallel to the aligned fibers.

Identify it by the silky, moving band of reflected light and golden-brown to reddish-brown coloration; unlike glass, it commonly shows fibrous bands and variable translucency. Typical specimens are a few dollars; quality cabochons or large polished pieces range from about $10–$75.