mineral

Tumbled dark pebble

Indeterminate; likely basalt or fine-grained dark metamorphic rock

AI-generated identification · may be incorrect

Black to dark gray, smoothly rounded and likely water-worn or tumbled; low to moderate luster, no visible crystals or cleavage. Estimated Mohs hardness 5–7; specific gravity roughly 2.7–3.1, but these cannot be confirmed from the image.

Identified August 13, 2026More mineral →

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Physical properties

Formation & geological history

Possibly a naturally weathered basalt pebble, formed from cooled mafic lava, or a dark metamorphic rock such as slate or amphibolite. Age and exact geological setting require testing or locality information.

Uses & applications

Used as a decorative pebble, landscaping stone, craft material, or aquarium substrate; specimens of this appearance generally have little commercial or jewelry value.

Geological facts

The uniformly smooth, oval shape indicates abrasion by water, sediment, or tumbling. A streak, hardness, magnetism, and fresh broken surface would help distinguish basalt from other dark rocks.

Field identification & locations

Common in volcanic and glacial terrains, beaches, riverbeds, and commercial tumbled-stone assortments. Basalt is typically dense and may contain tiny pale feldspar crystals; slate splits into sheets, while amphibolite may show granular crystals.