igneous

Tumbled gray pebble, likely basalt or dark chert

Most consistent with fine-grained basalt (plagioclase–pyroxene), though gray chert (microcrystalline SiO₂) is possible

AI-generated identification · may be incorrect

Smooth, rounded, dark gray, dull to faintly waxy luster, with no visible crystals or cleavage; estimated hardness 5.5–6.5 (basalt) or about 7 (chert), and specific gravity roughly 2.6–3.0.

Identified August 16, 2026More igneous →

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At a glance

Common name: Tumbled gray pebble, likely basalt or dark chert
Scientific name: Most consistent with fine-grained basalt (plagioclase–pyroxene), though gray chert (microcrystalline SiO₂) is possible
Category: igneous
Identified: August 16, 2026
Method: Standard

AI Estimated Value

About $1–$5 as a common tumbled or collected pebble; generally under $10 unless unusually attractive, locality-specific, or sold as part of a curated set.

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

Smooth, rounded, dark gray, dull to faintly waxy luster, with no visible crystals or cleavage; estimated hardness 5.5–6.5 (basalt) or about 7 (chert), and specific gravity roughly 2.6–3.0.

Formation & geological history

Likely naturally water-worn or mechanically tumbled from volcanic or siliceous rock; basalt commonly formed from rapidly cooled lava, generally ranging from Precambrian to modern in age.

Uses & applications

Commonly used as a decorative pebble, craft/tumbled stone, or landscaping material; ordinary specimens have little jewelry value.

Geological facts

The uniformly fine texture indicates rapid cooling or microcrystalline silica. A steel nail may scratch softer basalt but should not scratch chert; glass can help test higher hardness.

Field identification & locations

Common in streambeds, beaches, gravel deposits, and volcanic regions worldwide. A strong vinegar reaction would indicate carbonate rock instead, while a streak plate and hardness test can distinguish basalt from chert.