Rock Identifier
Tiger’s-eye (Chatoyant quartz (SiO₂), typically pseudomorphous quartz after crocidolite) — gemstone
gemstone

Tiger’s-eye

Chatoyant quartz (SiO₂), typically pseudomorphous quartz after crocidolite

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; golden-brown to reddish-brown color, silky vitreous luster, fibrous structure, and distinctive chatoyancy (cat’s-eye band) caused by aligned fibers. It has no prominent cleavage and specific gravity around 2.64–2.71.

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Physical properties

Hardness 6.5–7 Mohs; golden-brown to reddish-brown color, silky vitreous luster, fibrous structure, and distinctive chatoyancy (cat’s-eye band) caused by aligned fibers. It has no prominent cleavage and specific gravity around 2.64–2.71.

Formation & geological history

Forms when quartz replaces blue asbestos (crocidolite) fibers during low-temperature silicification, commonly in iron-rich metamorphic rocks. Much commercial material is Precambrian and comes from South Africa, Western Australia, India, Brazil, and Namibia.

Uses & applications

Cut and polished for cabochons, carvings, beads, ornaments, and inexpensive jewelry; rarely used decoratively as small specimens.

Geological facts

The golden color results from iron oxidation; blue-gray material is hawk’s-eye, while red-brown material is often called bull’s-eye. Chatoyancy is strongest when polished parallel to the fibers.

Field identification & locations

Identify it by its silky, moving light band, fibrous grain, and hardness greater than glass. Common localities include the Northern Cape of South Africa and Western Australia; avoid specimens with unnaturally uniform resin-like color.