mineral
Staurolite
Staurolite (Fe2Al9O6(SiO4)4(O,OH)2)
AI-generated identification · may be incorrectHardness of 7 to 7.5 on the Mohs scale, brownish-black to reddish-brown color, and a vitreous to resinous luster. It is well known for its characteristic cruciform twin crystals.
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Physical properties
Hardness of 7 to 7.5 on the Mohs scale, brownish-black to reddish-brown color, and a vitreous to resinous luster. It is well known for its characteristic cruciform twin crystals.
Formation & geological history
Forms in medium- to high-grade metamorphic rocks such as schists and gneisses through regional metamorphism of pelitic rocks.
Uses & applications
Used primarily as an index mineral in geology to determine metamorphic grade and collected as a novelty or talisman due to its natural cross shape.
Geological facts
Commonly known as fairy crosses or fairy stones, these specimens have inspired folklore and legends across many cultures for centuries.
Field identification & locations
Easily identified in the field by its distinct 60-degree or 90-degree penetration twinning forming crosses, found globally in schists alongside garnet and kyanite.
