igneous

Rounded gray river pebble, likely basalt or fine-grained volcanic rock

Probable basalt (fine-grained plagioclase–pyroxene rock); exact identification requires testing

AI-generated identification · may be incorrect

Dark gray, smoothly water-worn, dull to subtly satin luster, very fine-grained with no visible crystals; basalt hardness is about 6 Mohs, with poor/no cleavage and specific gravity around 2.8–3.0.

Identified August 22, 2026More igneous →

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At a glance

Common name: Rounded gray river pebble, likely basalt or fine-grained volcanic rock
Scientific name: Probable basalt (fine-grained plagioclase–pyroxene rock); exact identification requires testing
Category: igneous
Identified: August 22, 2026
Method: Standard

AI Estimated Value

Typically $1–$5 as a common natural pebble; up to about $10–$20 if unusually attractive, locally significant, or sold as a polished 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

Dark gray, smoothly water-worn, dull to subtly satin luster, very fine-grained with no visible crystals; basalt hardness is about 6 Mohs, with poor/no cleavage and specific gravity around 2.8–3.0.

Formation & geological history

Likely formed from rapidly cooled mafic lava, then rounded by stream or beach abrasion; its precise geological age and source cannot be determined from the photograph.

Uses & applications

Common basalt is used as crushed aggregate, road stone, paving, and landscaping; this small pebble has mainly decorative or teaching value rather than gem value.

Geological facts

A faint pale seam may be a mineral-filled fracture or vein, possibly quartz or calcite. Similar-looking gray pebbles can also be andesite, slate, or fine-grained metamorphic rock.

Field identification & locations

Check for tiny dark crystals, magnetic response, and a pale streak; a steel file should barely scratch it, while glass may be scratched by fresh basalt. Common in volcanic terrains and river or beach gravels.