Whiteschist

“Ultra-high-pressure rarity”

Metamorphic

Whiteschist is a rare metamorphic rock formed under ultra-high pressure conditions deep in subduction zones. Its pale color comes from minerals like talc and kyanite, and its existence provides evidence that continental crust can be subducted to extreme depths and then returned to the surface.

Composition

talc, kyanite, quartz, pyrope garnet, coesite

Where Found

Dora-Maira Massif (Italian Alps), Kokchetav Massif (Kazakhstan)

Mohs Hardness

4-7 (variable)

Fun Fact

Whiteschist from the Dora-Maira Massif contains coesite, a high-pressure form of quartz that only forms at depths greater than 100 km below Earth's surface.