Staurolite Schist
“Fairy crosses in foliated rock”
Staurolite schist is a medium-grade metamorphic rock containing distinctive staurolite crystals, which characteristically form cross-shaped twins. These 'fairy crosses' develop at specific temperature-pressure conditions, making staurolite an important index mineral for mapping metamorphic zones.
staurolite, garnet, muscovite, biotite, quartz, kyanite (occasional)
Fairy Stone State Park (Virginia, USA), Brittany (France), Keivy (Russia), Swiss Alps, Blue Ridge Mountains (USA)
7-7.5 (staurolite crystals)
According to Appalachian legend, fairies at the base of the Blue Ridge Mountains wept when they heard the news of Christ's crucifixion, and their tears crystallized into the cross-shaped staurolite stones.
Test Your Knowledge
Why is staurolite considered an important 'index mineral' in metamorphic petrology?
Photo Attribution
Title: Staurolite schist (Keivy Schist; Mt. Ploskaya, Kola Peninsula, Russia) 12.jpg
Author: James St. John
License: CC BY 2.0
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