metamorphic
Fairy Stone (Staurolite Twin)
Staurolite (Fe,Mg,Zn)2Al9Si4O22(OH)2
Hardness: 7-7.5. Color: Reddish-brown, brownish-black, or gray. Luster: Dull to vitreous. Crystal structure: Monoclinic (pseudo-orthorhombic). Cleavage: Distinct. Specific Gravity: 3.7-3.8.
- Hardness
- 7-7
- Color
- Reddish-brown, brownish-black, or gray
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7-7.5. Color: Reddish-brown, brownish-black, or gray. Luster: Dull to vitreous. Crystal structure: Monoclinic (pseudo-orthorhombic). Cleavage: Distinct. Specific Gravity: 3.7-3.8.
Formation & geological history
Forms during regional metamorphism of aluminous rocks like shale. Typically found in mica schists and gneisses across various geological ages, often forming as porphyroblasts.
Uses & applications
Used primarily as a collector's specimen and in jewelry (pendants). Historically used as a symbolic or religious talisman. Very minor use as an abrasive in sandblasting.
Geological facts
The name comes from the Greek word 'stauros' for cross. Legend says they are the petrified tears of fairies who wept after hearing of the crucifixion of Christ.
Field identification & locations
Identified by its characteristic 60-degree or 90-degree 'cross' twinning. Commonly found in Patrick County, Virginia (Fairy Stone State Park), Georgia, and the Alps. Look for dark, cruciform crystals protruding from softer schist matrix.
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