metamorphic
Polished dark river pebble, likely serpentinite or altered ultramafic rock
Serpentinite (predominantly serpentine-group minerals; identification is provisional)
AI-generated identification · may be incorrectDark olive-brown to black, smoothly tumbled/polished, with subdued waxy luster and mottled lighter patches. Serpentine has Mohs hardness about 2.5–4 and specific gravity around 2.5–2.6; crystal grains and cleavage are not visible in this rounded specimen.
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Physical properties
Dark olive-brown to black, smoothly tumbled/polished, with subdued waxy luster and mottled lighter patches. Serpentine has Mohs hardness about 2.5–4 and specific gravity around 2.5–2.6; crystal grains and cleavage are not visible in this rounded specimen.
Formation & geological history
Serpentinite forms when mantle-derived ultramafic rocks such as peridotite are hydrated during tectonic activity, commonly in ophiolite zones. The pebble was likely rounded by stream transport; its exact age cannot be determined visually.
Uses & applications
Used as ornamental stone, carvings, beads, and occasionally architectural material. This small polished piece has mainly educational or decorative value.
Geological facts
The appearance can overlap with polished basalt, chlorite-rich metamorphic rock, or dark jasper; a photograph alone cannot confirm the diagnosis.
Field identification & locations
The reported location in northeastern Bosnia is compatible with ophiolitic and metamorphic rocks, making serpentinite plausible. Check for a waxy feel, green undertones, and softness: it may scratch with a steel knife, unlike quartz-rich jasper.
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