metamorphic
Rounded dark river pebble, possibly serpentinite
Serpentinite (serpentine-group minerals; commonly lizardite/chrysotile/antigorite), identification tentative
AI-generated identification · may be incorrectDark greenish-black, smooth and water-worn, with subdued waxy-to-dull luster and irregular pale patches. Serpentinite has Mohs hardness about 2.5–4, no obvious cleavage, and density roughly 2.5–2.6; the image is insufficient for a firm mineral identification.
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Physical properties
Dark greenish-black, smooth and water-worn, with subdued waxy-to-dull luster and irregular pale patches. Serpentinite has Mohs hardness about 2.5–4, no obvious cleavage, and density roughly 2.5–2.6; the image is insufficient for a firm mineral identification.
Formation & geological history
Likely a naturally rounded stream or glacial pebble derived from altered ultramafic rock; serpentinization occurs when water alters peridotite. The specimen’s geological age cannot be determined visually.
Uses & applications
As a small pebble it has mainly collecting or ornamental value; serpentinite is also used decoratively as polished stone, though fibrous varieties may contain asbestos and should not be cut or abraded without testing.
Geological facts
A magnet, streak, hardness, and specific-gravity test would help distinguish serpentinite from basalt, slag, or dark chert. Avoid inhaling dust because some serpentinite can contain chrysotile.
Field identification & locations
The rounded form indicates transport in water. Around 44.4°N, 18.6°E in Bosnia and Herzegovina, serpentinite and other ophiolitic rocks are geologically plausible, but a dark basaltic or weathered ultramafic pebble is also possible.
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