metamorphic
Falcon's Eye (Blue Tiger's Eye)
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Dark blue to blue-gray or blue-green; Luster: Silky to vitreous; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64-2.71.
- Hardness
- 6
- Color
- Dark blue to blue-gray or blue-green
- Luster
- Silky to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Dark blue to blue-gray or blue-green; Luster: Silky to vitreous; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64-2.71.
Formation & geological history
Formed through a process called pseudomorphism, where quartz replaces the asbestos mineral crocidolite. Unlike Tiger's Eye, Falcon's Eye retains the original blue color of the crocidolite because it has not undergone the oxidation process that turns the iron yellow/brown.
Uses & applications
Primarily used as a gemstone in jewelry (cabochons, beads, rings), ornamental carvings, and by collectors for its unique silky chatoyancy.
Geological facts
Falcon's Eye is often called Blue Tiger's Eye. It is known for its 'chatoyancy' or cat's-eye effect, which is caused by the reflection of light off the parallel mineral fibers within the stone.
Field identification & locations
Identify in the field by its dark blue-gray color and distinctive silky bands that shimmer when moved under light. Most commonly found in South Africa, Australia, and Brazil.
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