Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Turquoise is an opaque, blue-to-green hydrous phosphate of copper and aluminum, often found in arid regions. Its color varies depending on the amount of copper (blue) and iron (green). Tiger's Eye is a chatoyant gemstone, typically golden to reddish-brown, formed by the silicification of crocidolite asbestos, resulting in a fibrous quartz structure that reflects light in a characteristic silky band.
How to Identify
- Color
- Turquoise: Sky blue, blue-green, apple green. Tiger's Eye: Golden yellow, golden brown, reddish-brown, sometimes blue (Hawk's Eye).
- Luster
- Turquoise: Waxy to subvitreous. Tiger's Eye: Silky, chatoyant.
- Texture
- Turquoise: Cryptocrystalline, massive, reniform, botryoidal. Tiger's Eye: Fibrous, compact.
- Crystal Form
- Turquoise: Rarely forms distinct crystals; typically massive, nodular, or as vein fillings. Tiger's Eye: Pseudomorph after fibrous crocidolite, maintaining the original fibrous structure.
- Cleavage
- Turquoise: Perfect on {001} (rarely observed due to cryptocrystalline nature). Tiger's Eye: None (due to fibrous quartz replacement).
- Geological Environment
- Turquoise: Secondary mineral in arid regions, often in altered volcanic or sedimentary rocks rich in aluminum, with copper mineralization. Tiger's Eye: Formed in metamorphic rocks, specifically in banded iron formations where crocidolite asbestos has been altered.
Key Facts
- Hardness: Turquoise: 5-6 on Mohs scale. Tiger's Eye: 6.5-7 on Mohs scale.
- Specific Gravity: Turquoise: 2.60-2.90. Tiger's Eye: 2.64-2.71.
- Crystal System: Turquoise: Triclinic. Tiger's Eye: Trigonal (as quartz pseudomorph).
- Color: Turquoise: Blue, blue-green, green. Tiger's Eye: Golden-yellow, golden-brown, reddish-brown, blue (Hawk's Eye).
- Luster: Turquoise: Waxy, subvitreous, dull. Tiger's Eye: Silky, chatoyant.
- Transparency: Turquoise: Opaque. Tiger's Eye: Opaque.
- Fracture: Turquoise: Conchoidal to uneven. Tiger's Eye: Splintery to conchoidal.
- Cleavage: Turquoise: Perfect on {001} (rarely observed). Tiger's Eye: None.
- Composition: Turquoise: Hydrous copper aluminum phosphate. Tiger's Eye: Silicon dioxide (SiO2) with fibrous inclusions of iron oxides.
Quick Check
- Color: Turquoise: Blue to green. Tiger's Eye: Golden-brown, yellow, red-brown, blue.
- Luster: Turquoise: Waxy to subvitreous. Tiger's Eye: Silky, chatoyant.
- Streak: Turquoise: White to pale blue-green. Tiger's Eye: Yellowish-brown.
Physical Characteristics
- Crystal Habit: Turquoise: Massive, cryptocrystalline, reniform, botryoidal, stalactitic, encrusting. Tiger's Eye: Fibrous aggregates, pseudomorphs after crocidolite.
- Cleavage Type: Turquoise: Perfect on {001} (rarely seen). Tiger's Eye: None.
- Fracture Type: Turquoise: Conchoidal to uneven. Tiger's Eye: Splintery to conchoidal.
- Tenacity: Turquoise: Brittle. Tiger's Eye: Brittle.
- Luster Type: Turquoise: Waxy, subvitreous, dull. Tiger's Eye: Silky, chatoyant.
Formation
Turquoise: A secondary mineral formed by the percolation of acidic, copper-rich waters through aluminum-rich rocks. It precipitates in fractures and cavities. Tiger's Eye: A pseudomorph of quartz after the fibrous mineral crocidolite (a blue asbestos). Silica-rich solutions replace the crocidolite, preserving its fibrous structure, which causes the chatoyancy.
Usage
Both are highly valued as gemstones for jewelry and ornamental objects. Turquoise has historical and cultural significance in many ancient civilizations. Tiger's Eye is popular for its unique optical effect.
Age Distribution
Turquoise: Formed in arid regions, often associated with secondary copper deposits, typically Cenozoic to Mesozoic. Tiger's Eye: Formed from alteration of Precambrian crocidolite asbestos.
Where to Find
Turquoise: Southwestern United States (Arizona, Nevada, New Mexico)
Historically significant deposits, particularly in Arizona (Sleeping Beauty, Kingman mines) and Nevada (Lander Blue, Carico Lake).
Turquoise: Iran (Persia)
Nishapur district, renowned for its high-quality, intense blue 'Persian Turquoise'.
Turquoise: China (Hubei province)
Significant producer of various qualities of turquoise.
Turquoise: Egypt (Sinai Peninsula)
Ancient mines, particularly Serabit el-Khadim and Wadi Maghareh.
Tiger's Eye: South Africa (Griqualand West)
The primary and most significant source of high-quality Tiger's Eye.
Tiger's Eye: Australia (Western Australia)
Notable deposits, often associated with banded iron formations.
Tiger's Eye: India, Myanmar, Namibia, United States (California)
Smaller deposits and occurrences.
Finding Tips
Turquoise: Look for host rock
Turquoise is typically found in veins, nodules, or crusts within altered igneous or sedimentary rocks, often associated with limonite or other iron oxides.
Turquoise: Color and matrix
High-quality turquoise has an even, intense blue color. The presence of a 'matrix' (host rock inclusions, often black or brown limonite) can be a distinguishing feature, sometimes enhancing its aesthetic appeal.
Tiger's Eye: Identify chatoyancy
The most distinctive feature is the silky, shifting band of light (chatoyancy) that moves across the surface when the stone is rotated. This is due to the parallel fibrous structure.
Tiger's Eye: Observe color variations
Tiger's Eye typically exhibits golden-yellow to reddish-brown hues. Blue varieties (Hawk's Eye) are less oxidized. Red Tiger's Eye is often heat-treated.
Safety Warning for Tiger's Eye (Crocidolite Origin)
Tiger's Eye is a pseudomorph of quartz after crocidolite asbestos. While the asbestos has been completely replaced by quartz and is no longer in its fibrous, hazardous form, it is crucial to understand its origin. Intact, polished Tiger's Eye is generally considered safe to handle. However, avoid grinding, cutting, or polishing raw, un-silicified crocidolite or even raw Tiger's Eye without proper respiratory protection, as this could release microscopic silica dust or residual asbestos fibers (though highly unlikely in fully silicified material). Always err on the side of caution with any material derived from asbestos.
Similar Rocks
Chrysocolla
CuSiO3·nH2O
Also known as: Gem silica
Variscite
AlPO4·2H2O
Also known as: Utahlite
Hawk's Eye
Fibrous crocidolite replaced by chalcedony (less oxidized than Tiger's Eye)
Also known as: Blue Tiger's Eye
Serpentine
(Mg,Fe)3Si2O5(OH)4
Also known as: New Jade
Scientific Classification
- Mineral Class
- Turquoise: Phosphates. Tiger's Eye: Silicates (specifically tectosilicates, quartz group).
- Group
- Turquoise: Turquoise group. Tiger's Eye: Quartz group (chalcedony variety).
- Crystal System
- Turquoise: Triclinic. Tiger's Eye: Trigonal (as quartz pseudomorph).
- Chemical Formula
- Turquoise: CuAl6(PO4)4(OH)8·4H2O. Tiger's Eye: SiO2 (with fibrous inclusions of iron oxides, pseudomorph after Na2(Fe2+,Mg)3Fe3+2Si8O22(OH)2).
- Composition
- Turquoise: Copper, aluminum, phosphorus, oxygen, hydrogen. Tiger's Eye: Silicon, oxygen, with iron impurities.
Explore Turquoise and Tiger's Eye
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.