Rock Identifier
Tiger's Eye / Hawk's Eye (Pseudomorph of Quartz after Crocidolite (SiO2)) — mineral
mineral

Tiger's Eye / Hawk's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Blue-grey (Hawk's Eye) and Golden-brown (Tiger's Eye); Luster: Silky; Crystal Structure: Trigonal (fibrous aggregate); Cleavage: None; Specific Gravity: 2.64-2.71.

Hardness
6
Color
Blue-grey (Hawk's Eye) and Golden-brown (Tiger's Eye)
Luster
Silky
Identified More mineral

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Blue-grey (Hawk's Eye) and Golden-brown (Tiger's Eye); Luster: Silky; Crystal Structure: Trigonal (fibrous aggregate); Cleavage: None; Specific Gravity: 2.64-2.71.

Formation & geological history

Formed through a pseudomorphic process where silica (quartz) replaces the fibrous mineral crocidolite. It typically forms in metamorphic environments within iron formations. This specific piece shows a transition between Blue Hawk's Eye and Golden Tiger's Eye.

Uses & applications

Widely used in jewelry making (cabochons, beads), decorative carvings, and as a popular collector's stone due to its chatoyancy.

Geological facts

It exhibits 'chatoyancy', a cat-eye effect caused by the reflection of light off the parallel fibrous structure. The golden color in Tiger's Eye is caused by the oxidation of iron within the crocidolite fibers, whereas blue Hawk's Eye remains unoxidized.

Field identification & locations

Identified in the field by its distinct parallel bands and shifting 'silk' luster when tilted. Major sources include South Africa, Australia, Burma, and Namibia. Collectors value pieces with sharp bands and mixed colors.