metamorphic

Greenstone (likely altered basalt or metabasalt)

Chlorite–actinolite-rich metabasalt; composition commonly dominated by chlorite, actinolite, epidote, albite, and quartz

AI-generated identification · may be incorrect

Typically dark green to gray-green, fine-grained, opaque, and dull to weakly silky; hardness about 5–6 Mohs, massive texture, poor cleavage, and specific gravity roughly 2.8–3.2. The specimen appears weathered and may contain rusty iron-oxide staining.

Identified September 5, 2026More metamorphic →

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At a glance

Common name: Greenstone (likely altered basalt or metabasalt)
Scientific name: Chlorite–actinolite-rich metabasalt; composition commonly dominated by chlorite, actinolite, epidote, albite, and quartz
Category: metamorphic
Identified: September 5, 2026
Method: Standard

AI Estimated Value

About $2–$15 for a hand specimen; polished or unusually attractive pieces may reach $20–$50.

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

Forms when basaltic lava or mafic volcanic rock undergoes low-grade greenschist-facies metamorphism, commonly during Precambrian to Phanerozoic tectonic alteration. Exact age cannot be determined from the photograph.

Uses & applications

Used locally as crushed aggregate, landscaping stone, building stone, and occasionally as a polished ornamental material; generally little gem value.

Geological facts

“Greenstone” is a field and commercial term rather than one precise mineral species; similar-looking material may also be serpentinite or chlorite-rich basalt.

Field identification & locations

Identify by its uniform green color, fine massive texture, lack of visible large crystals, and moderate hardness; a streak, acid, magnetism, and thin-section test would help distinguish it from serpentinite or jade. Common in metamorphic belts and altered volcanic terrains worldwide.