metamorphic
Tumbled dark stone, possibly serpentinite
Serpentinite (serpentine-group minerals; commonly Mg₃Si₂O₅(OH)₄)
AI-generated identification · may be incorrectDark olive-brown to black, waxy/submetallic luster, irregular massive texture, and no visible crystal faces or cleavage. Serpentine has Mohs hardness about 2.5–4 and specific gravity roughly 2.5–2.6; the photograph alone cannot exclude a dark basalt, slag, or another tumbled stone.
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Physical properties
Dark olive-brown to black, waxy/submetallic luster, irregular massive texture, and no visible crystal faces or cleavage. Serpentine has Mohs hardness about 2.5–4 and specific gravity roughly 2.5–2.6; the photograph alone cannot exclude a dark basalt, slag, or another tumbled stone.
Formation & geological history
Serpentinite forms when ultramafic mantle rocks hydrate during hydrothermal alteration, commonly along tectonic plate boundaries; its age depends on the host ophiolite. Rocks of this general type are geologically plausible near 44.4°N, 18.6°E, where ophiolitic and metamorphic rocks occur in Bosnia and Herzegovina.
Uses & applications
Used as an ornamental and carving stone, aggregate, and historically as a source of decorative “green marble”; attractive polished pieces are sold as lapidary material.
Geological facts
A stronger identification would require a fresh surface, streak, hardness test, magnet test, and ideally density or Raman/XRF analysis. Avoid creating dust, since some serpentinites may contain asbestos-form minerals.
Field identification & locations
Look for a greasy or waxy feel, mottled green-black color, low hardness, and occasional fibrous veining. Common occurrences include Alpine-type ophiolites and ultramafic belts; this small rounded specimen appears tumbled or naturally water-worn.
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