Greenschist

“Metamorphism's green signature”

Metamorphic

Greenschist is a foliated metamorphic rock characterized by its green color, which comes from abundant chlorite, epidote, and actinolite minerals. It forms under moderate temperatures and pressures, representing an important zone in the metamorphic progression from slate to higher-grade rocks.

Composition

chlorite, epidote, actinolite, albite, quartz

Where Found

Vermont (USA), Swiss Alps, Scottish Highlands, Barberton Greenstone Belt (South Africa)

Mohs Hardness

4-5

Fun Fact

The entire 'greenschist facies' — a major classification of metamorphic conditions — is named after this rock, which defines conditions of roughly 300-500°C.