Whiteschist (Talc-Kyanite)
“Ultra-high pressure record-holder”
Talc-kyanite whiteschist is a rare, pale metamorphic rock that forms under ultra-high pressure conditions exceeding 3 GPa — corresponding to depths of over 100 km. The unlikely coexistence of talc and kyanite requires extremely magnesian bulk compositions and records subduction to exceptional depths.
talc, kyanite, pyrope garnet, coesite, phengite, rutile
Dora-Maira Massif (Western Alps, Italy), Kokchetav Massif (Kazakhstan), limited occurrences in ultra-high pressure terranes
4-7 (variable by mineral)
The discovery of coesite (high-pressure quartz) in Dora-Maira whiteschist in 1984 revolutionized geology by proving that continental crust could be subducted to mantle depths and return intact — previously thought impossible.
Test Your Knowledge
Why was the discovery of coesite in Dora-Maira whiteschist revolutionary for plate tectonics theory?
Related Specimens
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