metamorphic

Greenstone (Epidosite/Altered Diorite)

Metabasalt or Meta-andesite / Epidotized Diorite

AI-generated identification · may be incorrect

Hardness: 6-7 Mohs; Color: Dull green, olive to sage green with white/pinkish plagioclase flecks and dark hornblende; Luster: Dull to waxy; Texture: Fine to medium-grained; Cleavage: Poor

Hardness: 6-7 Mohs
Luster: Dull to waxy

Identified July 15, 2026More metamorphic →

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Physical properties

Hardness: 6-7 Mohs; Color: Dull green, olive to sage green with white/pinkish plagioclase flecks and dark hornblende; Luster: Dull to waxy; Texture: Fine to medium-grained; Cleavage: Poor

Formation & geological history

Formed through low-grade regional metamorphism (greenschist facies) of mafic to intermediate igneous rocks. The green color comes from the alteration of minerals to epidote, chlorite, and actinolite.

Uses & applications

Primarily used as river rock for landscaping, decorative gravel, or in road construction. Some high-quality specimens are used in lapidary for polishing or carving.

Geological facts

Greenstone is a general field term for any dark, greenish-colored altered igneous rock. It is a major component of 'Greenstone Belts' which contain some of Earth's oldest rocks and significant gold deposits.

Field identification & locations

Commonly found in riverbeds and glacial tills. Identify by its distinct greenish hue that remains even when dry, and its high hardness (won't be scratched by a steel knife). Commonly found in the Pacific Northwest and Great Lakes regions.