Tiger's eye, iron eye, hawk's eye, bull's eye

Tiger's eye, iron, hawk's, and bull's eye are varieties of fibrous quartz, characterized by a shimmering effect called cat's eye, produced by the reflection of light on the mineral fibers and inclusions.

Tiger's Eye: Golden-brown to yellow quartz, whose silky reflections are linked to crocidolite fibers altered into iron oxides.

Hawk's Eye: A gray-blue to blue-green variety, corresponding to a less oxidized stage of tiger's eye, with crocidolite fibers still preserved.

Iron Eye: A natural combination of tiger's eye, hematite, and jasper, typically featuring red, brown, golden, and black bands.

Bull's Eye: A red to reddish-brown variety, usually obtained when tiger's eye undergoes natural or artificial heat treatment, which intensifies the red and brown tones.