metamorphic
Hawk's Eye / Pietersite (Tiger's Eye variant)
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Dark blue-grey to blue-green with golden/brown streaks; Luster: Silky/Vitreous; Structure: Fibrous quartz; Chatoyancy (shimmer effect)
- Hardness
- 6
- Color
- Dark blue-grey to blue-green with golden/brown streaks
- Luster
- Silky/Vitreous
Identified More metamorphic →
Explore Hawk's Eye / Pietersite (Tiger's Eye variant) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Dark blue-grey to blue-green with golden/brown streaks; Luster: Silky/Vitreous; Structure: Fibrous quartz; Chatoyancy (shimmer effect)
Formation & geological history
Formed through the pseudomorphism of crocidolite (asbestos) by silica. Hawk's eye is the blue, less altered precursor to the more common golden Tiger's Eye. Pietersite is a brecciated form combining both.
Uses & applications
Primarily used in jewelry as cabochons, for ornamental carvings, and by mineral collectors for its unique optical properties.
Geological facts
The shimmering effect, called chatoyancy, occurs because the fibrous structure of the original crocidolite mineral is preserved even after it is replaced by quartz. Hawk's eye is often referred to as 'Blue Tiger's Eye.'
Field identification & locations
Look for the chatoyant 'cat's eye' effect when moving the stone under a light source. Found primarily in South Africa and Namibia. Tumbled specimens are distinguished by their dark blue-black base and silky sheen.
More like this
