How to identify Tiger's Eye (Blue and Gold)
Quartz (fibrous crocidolite replaced by chalcedony)
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Open the appTo correctly identify Tiger's Eye (Blue and Gold) (Quartz (fibrous crocidolite replaced by chalcedony)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.
Step-by-step identification
- 1
Color
Overall color and any zoning or banding
Golden-brown to reddish-brown (gold Tiger's Eye); blue-gray to blue-green (blue Tiger's Eye/Hawk's Eye). Often banded or streaked.
- 2
Luster
How the surface reflects light: metallic, vitreous, dull
Silky to vitreous, with a distinct chatoyancy.
- 3
Texture
Grain size and surface feel: coarse, fine, glassy
Fine-grained, fibrous appearance, often with a smooth, polished feel when cut and polished.
- 4
Crystal Form
Shape of visible crystals or crystal faces
Massive, fibrous aggregates, pseudomorphing original crocidolite fibers. Does not typically form macroscopic crystals of quartz.
- 5
Cleavage
How it breaks: flat cleavage planes vs irregular fracture
None, as it is a cryptocrystalline variety of quartz.
- 6
Geological Environment
The rock formation and setting where it occurs
Formed in metamorphic environments, typically within banded iron formations or other iron-rich sedimentary rocks, where crocidolite asbestos was originally present.
Key Facts
- Hardness
- 7 (Mohs scale)
- Specific Gravity
- 2.64 - 2.71
- Crystal System
- Trigonal (cryptocrystalline)
- Color
- Golden-brown, reddish-brown, blue-gray, blue-green
- Luster
- Silky, vitreous, chatoyant
- Transparency
- Opaque to translucent
- Fracture
- Conchoidal to splintery
- Cleavage
- None
- Composition
- Silicon dioxide (SiO2) with fibrous inclusions of iron oxides (limonite/goethite) or unoxidized crocidolite.
Physical characteristics
- Crystal Habit: Massive, fibrous aggregates, pseudomorphic after crocidolite.
- Cleavage Type: None
- Fracture Type: Conchoidal to splintery
- Tenacity: Brittle
- Luster Type: Silky to vitreous, with strong chatoyancy
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