metamorphic
Tumbled black-and-gold tiger’s-eye
Quartz pseudomorph after crocidolite; SiO₂ with iron oxides
AI-generated identification · may be incorrectMohs hardness 6.5–7; opaque brown-black to golden-brown, vitreous to silky chatoyant luster, with fibrous bands and no obvious cleavage. The polished surface shows tiger-eye chatoyancy, though this piece is unusually dark and may include iron-rich alteration or related jasper.
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Physical properties
Mohs hardness 6.5–7; opaque brown-black to golden-brown, vitreous to silky chatoyant luster, with fibrous bands and no obvious cleavage. The polished surface shows tiger-eye chatoyancy, though this piece is unusually dark and may include iron-rich alteration or related jasper.
Formation & geological history
Forms when quartz replaces fibrous crocidolite during low-grade metamorphism and weathering, preserving its fibrous structure; major deposits are Precambrian, especially in South Africa and Western Australia.
Uses & applications
Used for cabochons, beads, carvings, tumbled stones, and ornamental objects; valued mainly as an attractive lapidary material rather than a rare gemstone.
Geological facts
Its moving band of reflected light is caused by aligned fibers and internal interfaces, producing the cat’s-eye effect known as chatoyancy. Blue-gray hawk’s-eye commonly represents an earlier stage of alteration.
Field identification & locations
Identify it by silky parallel bands, brown-gold colors, opaque quartz-like hardness, and a bright reflective stripe when rotated under a focused light. Common localities include South Africa, Australia, India, Brazil, and Namibia.
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