metamorphic

Greenstone

Metabasalt / Chlorite Schist

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Dull green, dark forest green to grayish-green; Luster: Earthy to waxy; Crystal Structure: Very fine-grained, microcrystalline; Cleavage: None (subconchoidal fracture); Specific Gravity: 2.8-3.0

Hardness: 6-7 on Mohs scale
Color: Dull green, dark forest green to grayish-green
Luster: Earthy to waxy

Identified June 29, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed through the low-grade metamorphism (greenschist facies) of mafic igneous rocks like basalt. Subjected to heat and pressure, original minerals transform into chlorite, actinolite, and epidote. Often associated with ancient oceanic crust or mountain-building events.

Uses & applications

Historically used for making stone axes and tools due to its toughness. Today used as crushed stone for road construction, architectural stone accents, ornate carvings, and decorative gravel.

Geological facts

The green color is primarily due to the presence of chlorite, actinolite, and epidote. In some regions like British Columbia and New Zealand, high-quality greenstone is referred to as 'Pounamu' and holds great cultural significance.

Field identification & locations

Identify in the field by its distinct green hue, extreme toughness, and lack of obvious layering compared to slate. Commonly found in coastal areas, river beds near tectonic plate boundaries, and ancient mountain belts.