metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxide inclusions)
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown; Luster: Silky; Crystal structure: Trigonal (fibrous aggregate); Cleavage: None; Specific gravity: 2.64–2.71.
- Hardness
- 6
- Color
- Golden yellow to deep brown
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown; Luster: Silky; Crystal structure: Trigonal (fibrous aggregate); Cleavage: None; Specific gravity: 2.64–2.71.
Formation & geological history
Formed through a process called pseudomorphism, where microcrystalline quartz replaces the fibrous mineral crocidolite (blue asbestos). During this transition, iron is oxidized to produce the characteristic golden coloration. It is often found in banded iron formations of Precambrian age.
Uses & applications
Primarily used in jewelry (cabochons, beads), decorative carvings, and as a semi-precious gemstone for collectors and metaphysical belief practices.
Geological facts
It is famous for its 'chatoyancy' (the cat's-eye effect), which is caused by the reflection of light off the parallel mineral fibers within the stone. When the iron doesn't oxidize during formation, the stone remains blue and is called 'Hawk's Eye'.
Field identification & locations
Identified in the field by its distinct parallel golden-brown bands and the shimmer (chatoyancy) that moves when the stone is tilted. Significant deposits are found in South Africa (Northern Cape), Australia, India, and Namibia.
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