metamorphic
Tumbled tiger’s-eye-rich quartzite
Quartzite, composed mainly of microcrystalline quartz (SiO₂) with fibrous crocidolite pseudomorphs and iron oxides
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7, vitreous to silky luster, brown-gold chatoyant bands, and massive texture without obvious cleavage; the rounded surface is mechanically polished. Gray areas may be quartz-rich host rock or altered material.
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Physical properties
Typically Mohs hardness 6.5–7, vitreous to silky luster, brown-gold chatoyant bands, and massive texture without obvious cleavage; the rounded surface is mechanically polished. Gray areas may be quartz-rich host rock or altered material.
Formation & geological history
Formed when quartz-rich rock recrystallized during metamorphism, with former crocidolite fibers replaced by quartz and iron oxides producing golden-brown color and chatoyancy. Tiger’s eye deposits are commonly Precambrian, especially in South Africa and Western Australia.
Uses & applications
Used for cabochons, carvings, beads, ornamental stone, and inexpensive collector specimens; rarely used as architectural stone.
Geological facts
The silky reflective effect is called chatoyancy (“cat’s-eye” effect), caused by aligned fibrous inclusions. Blue-gray hawk’s-eye may represent an incompletely oxidized stage of tiger’s eye.
Field identification & locations
Identify it by parallel golden bands, silky reflective sheen when rotated, high hardness, and resistance to scratching by a steel knife; quartz-rich specimens should scratch glass. Common sources include South Africa, Australia, India, Brazil, and the United States.
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