Greenschist

Physical Properties

Hardness: 3.5-4.5 on Mohs scale; Color: Greenish-grey with mottled tan patches; Luster: Dull to silky; Crystal Structure: Foliated/Schistose; Cleavage: Good in one direction; Specific Gravity: 2.8-3.3

Formation & Geological History

Formed through regional metamorphism of mafic igneous rocks (like basalt) under low-temperature (200-450 C) and moderate-pressure conditions. Usually associated with orogenic belts.

Uses & Applications

Used as decorative stone in gardens, for architectural facings, and occasionally as a source for minor minerals or construction aggregate.

Geological Facts

The green color is primarily due to minerals like chlorite, epidote, and actinolite. The name 'greenschist' refers specifically to the green color and the schistose (layered) texture.

Field Identification & Locations

Look for the characteristic green hue and fine-grained, foliated layers that may appear platy. It is common in ancient mountain belts and coastal regions where oceanic crust has been subducted.

Identified on: 5/3/2026

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