igneous
Small dark tumbled stone, possibly basalt or serpentinite
Uncertain from image; likely fine-grained basalt (plagioclase and pyroxene) or dark serpentinite (serpentine-group minerals)
AI-generated identification · may be incorrectDark gray-green, opaque, with a matte-to-waxy luster and rounded, polished edges; estimated Mohs hardness 5–6 for basalt or 2.5–5.5 for serpentinite. No visible crystals, cleavage, or diagnostic texture at this scale.
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Physical properties
Dark gray-green, opaque, with a matte-to-waxy luster and rounded, polished edges; estimated Mohs hardness 5–6 for basalt or 2.5–5.5 for serpentinite. No visible crystals, cleavage, or diagnostic texture at this scale.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, while serpentinite forms when mantle-derived ultramafic rocks are hydrated; ages vary widely by locality.
Uses & applications
Commonly used as a decorative or educational specimen, aggregate, and landscaping stone; serpentinite may also be carved or polished. This small piece has minimal commercial value.
Geological facts
The image does not show enough detail for reliable species-level identification; a streak, hardness, magnetism, and close-up texture test would help distinguish basalt from serpentinite or another dark stone.
Field identification & locations
Look for basalt’s fine grain and occasional tiny pale crystals, or serpentinite’s waxy surface and green veining; common sources include volcanic regions and ophiolite belts. Avoid acid testing unless necessary.
