How to identify Tiger's Eye
Tiger's Eye (variety of Chalcedony, a cryptocrystalline form of Quartz)
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Open the appTo correctly identify Tiger's Eye (Tiger's Eye (variety of Chalcedony, a cryptocrystalline form of Quartz)), 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-yellow, golden-brown, reddish-brown, sometimes with darker bands. Hawk's Eye (blue Tiger's Eye) is blue to bluish-green.
- 2
Luster
How the surface reflects light: metallic, vitreous, dull
Silky to vitreous, exhibiting strong chatoyancy.
- 3
Texture
Grain size and surface feel: coarse, fine, glassy
Fine-grained, fibrous appearance internally, often polished smooth externally.
- 4
Crystal Form
Shape of visible crystals or crystal faces
Massive, fibrous aggregates, typically found as veins or layers within host rock. Does not form macroscopic crystals.
- 5
Cleavage
How it breaks: flat cleavage planes vs irregular fracture
None, due to its cryptocrystalline nature.
- 6
Geological Environment
The rock formation and setting where it occurs
Typically found in highly metamorphosed iron formations, often associated with asbestos deposits. It forms in veins or layers within these rocks where crocidolite has been altered by silica-rich hydrothermal fluids.
Key Facts
- Hardness
- 6.5-7 on the Mohs scale
- Specific Gravity
- 2.64-2.71
- Crystal System
- Trigonal (as quartz)
- Color
- Golden-yellow, golden-brown, reddish-brown, blue (Hawk's Eye)
- Luster
- Silky to vitreous, chatoyant
- Transparency
- Opaque to translucent
- Fracture
- Conchoidal to splintery
- Cleavage
- None
- Composition
- Silicon dioxide (SiO2) with fibrous inclusions of iron-stained amphibole (originally crocidolite)
Physical characteristics
- Crystal Habit: Massive, fibrous aggregates, pseudomorphous after crocidolite.
- Cleavage Type: None
- Fracture Type: Conchoidal to splintery, due to its cryptocrystalline nature and fibrous structure.
- Tenacity: Brittle
- Luster Type: Silky (due to fibrous inclusions) to vitreous (of the quartz matrix)
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