Greenschist (Greenstone)

Physical Properties

Hardness: 3.5-4.5 (Mohs); Color: Pale green to dark green with white/gray mottling; Luster: Dull to pearly; Crystal structure: Foliated or massive with platy mineral grains; Specific Gravity: 2.8–3.0.

Formation & Geological History

Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt) under low temperatures and high pressures. This process typically occurs in subduction zones or orogenic belts where tectonic plates collide.

Uses & Applications

Used primarily as decorative stone, crushed stone for construction, and sometimes for sculpture. High-quality slabs are used for garden landscaping and flagstone.

Geological Facts

The green color comes from the presence of green minerals like chlorite, epidote, and actinolite. It is a key indicator for geologists of the 'Greenschist Facies' metamorphic environment.

Field Identification & Locations

Identify in the field by its distinct grayish-green hue and sometimes a 'schistose' texture where it splits into flakey layers. It is commonly found in mountain ranges and accretionary prisms like the Appalachian Mountains or the Alps.

Identified on: 4/23/2026

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