metamorphic

Greenstone, likely altered basalt

Metabasalt (chlorite–actinolite–epidote assemblage), likely greenschist-facies greenstone

AI-generated identification · may be incorrect

Fine-grained, dull green to gray-green, massive and weakly foliated with a rough texture; typical hardness is about 5–6 Mohs, with no obvious cleavage and a granular/interlocking crystal structure. Green color commonly comes from chlorite, actinolite, epidote, and altered pyroxene.

Identified August 20, 2026More metamorphic →

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At a glance

Common name: Greenstone, likely altered basalt
Scientific name: Metabasalt (chlorite–actinolite–epidote assemblage), likely greenschist-facies greenstone
Category: metamorphic
Identified: August 20, 2026
Method: Standard

AI Estimated Value

$1–$10 for a common hand specimen; approximately $10–$40 if unusually attractive, polished, or sold as a documented locality specimen.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when basaltic lava was metamorphosed by low- to medium-grade heat and pressure, commonly during mountain building or oceanic-crust alteration. Its exact age cannot be determined from the photograph; greenstone occurs from Precambrian to modern tectonic belts.

Uses & applications

Used locally as crushed aggregate, road stone, landscaping rock, and historically for tools or ceremonial objects; attractive polished pieces are collectible but are generally not jewelry-grade.

Geological facts

“Greenstone” is a field term rather than one precise mineral or rock species, and appearance alone cannot distinguish metabasalt from altered volcanic rock or serpentinite.

Field identification & locations

Look for a dark green, fine-grained, heavy rock that is harder than most sedimentary rocks; a streak test, magnetism, acid reaction, and thin-section or XRF analysis improve identification. Common settings include ancient volcanic belts and metamorphic terrains worldwide.