metamorphic
Tiger’s-eye (likely red/brown variety)
Chatoyant quartz, chiefly SiO₂, pseudomorphous after crocidolite (riebeckite)
AI-generated identification · may be incorrectHardness 6.5–7; brown, reddish-brown, and black fibrous bands with a silky chatoyant sheen when polished. Quartz has a trigonal crystal structure, no cleavage, and specific gravity near 2.65; this appears as a rough-cut slab with a polished face.
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Physical properties
Hardness 6.5–7; brown, reddish-brown, and black fibrous bands with a silky chatoyant sheen when polished. Quartz has a trigonal crystal structure, no cleavage, and specific gravity near 2.65; this appears as a rough-cut slab with a polished face.
Formation & geological history
Forms when quartz replaces parallel crocidolite fibers during low-grade metamorphism and silicification, commonly in Precambrian iron-rich formations. Major deposits are associated with the Transvaal Supergroup of South Africa and similar terrains.
Uses & applications
Used for cabochons, carvings, ornamental slabs, bookends, and decorative objects; attractive chatoyant material is used in jewelry.
Geological facts
Red tiger’s-eye is often called bull’s-eye or ox-eye, while untreated golden tiger’s-eye is the classic variety. The visible parallel bands produce a moving reflective “eye” under directional light.
Field identification & locations
Identify by its parallel fibrous bands, vitreous-to-silky luster, quartz-like hardness, and chatoyancy; iron staining produces red tones. Common sources include South Africa, Western Australia, India, and Namibia.
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