Tiger's Eye

Hardness: 6.5-7 on the Mohs scale. Color: Golden brown to reddish-brown, often with shimmering bands. Luster: Silky to chatoyant. Crystal Structure: Trigonal (as quartz pseudomorph after crocidolite). Specific Gravity: 2.64-2.71. Shows chatoyancy, a movable lustrous band that resembles the eye of a cat, which is caused by the parallel intergrowth of quartz and altered amphibole fibers.

Tiger's Eye forms when quartz pseudomorphically replaces crocidolite (a fibrous blue amphibole mineral). The original crocidolite fibers are composed of iron and magnesium, and during the replacement process, the iron oxidizes, giving Tiger's Eye its distinctive golden to reddish-brown colors. The fibrous structure of the crocidolite is preserved by the quartz, leading to the chatoyant effect. This process typically occurs in metamorphic environments within certain types of iron formations. Its geological age varies, but it is often found in significantly old geological formations.

Predominantly used as a gemstone in jewelry (beads, cabochons, carvings) due to its unique chatoyancy and attractive colors. It is also used in ornamental objects and as a decorative stone. Historically, it was sometimes used as an amulet or charm.

Tiger's Eye is a member of the quartz family. A closely related mineral is Hawk's Eye (or Blue Tiger's Eye), where the crocidolite has not been completely replaced by quartz or limonite, resulting in a blue-grey color. Red Tiger's Eye is often heat-treated Tiger's Eye, as heating enhances the red hues by further oxidizing the iron. The 'eye' effect (chatoyancy) moves across the surface of the stone as it is rotated.

Tiger's Eye is commonly found in South Africa (especially in the Northern Cape province, which is a major source), Australia, India, and the USA (Arizona). In the field, look for its distinctive golden-brown to reddish-brown color and the characteristic silky chatoyancy that appears as a shimmering band. It often occurs in massive form within metamorphosed banded iron formations. Collectors look for stones with a strong, sharp 'eye' effect and vibrant, well-defined color bands. It will scratch glass, indicating its hardness, and typically won't react to common household acids.