metamorphic

Greenstone (Epidosite)

Epidosite (Metamorphosed Basalt/Diabase)

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale), Color: Pistachio green to dark gray-green, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (subconchoidal fracture), Specific Gravity: 3.2-3.5

Identified July 4, 2026More metamorphic →

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Physical properties

Hardness: 6-7 (Mohs scale), Color: Pistachio green to dark gray-green, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (subconchoidal fracture), Specific Gravity: 3.2-3.5

Formation & geological history

Formed through the low-grade metamorphism of mafic igneous rocks (like basalt or diabase) in hydrothermal environments or subduction zones, typically during the Paleozoic or Mesozoic eras.

Uses & applications

Used primarily as decorative river stones, landscaping materials, and occasionally in stone carving or as a lapidary material for cabochons.

Geological facts

Greenstone is a general field term for any dark, greenish, altered igneous rock. The green color is primarily due to the presence of minerals like epidote, chlorite, and actinolite.

Field identification & locations

Identify by its characteristic 'pistachio' green patches and high density. Commonly found in riverbeds near ancient mountain ranges (like the Appalachians or Cascades). Collectors look for smooth, water-worn cobbles with high epidote content.