igneous
Dark rounded stone, possibly basalt
Basalt (tentative; fine-grained mafic volcanic rock)
AI-generated identification · may be incorrectThe specimen appears dark gray to brown, opaque, and dull to faintly earthy, with an irregular rounded shape. Basalt typically has Mohs hardness 5–6, no obvious cleavage, fine interlocking crystals, and specific gravity about 2.8–3.0.
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Physical properties
The specimen appears dark gray to brown, opaque, and dull to faintly earthy, with an irregular rounded shape. Basalt typically has Mohs hardness 5–6, no obvious cleavage, fine interlocking crystals, and specific gravity about 2.8–3.0.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools rapidly at or near Earth’s surface, commonly in volcanic flows and oceanic crust. Its exact age cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, road stone, concrete aggregate, and occasionally as decorative stone. This small, unpolished piece has little jewelry or commercial value.
Geological facts
The image is too low-resolution for definitive identification; dark stones may also be weathered andesite, scoria, chert, or slag. Basalt is among Earth’s most abundant crustal rocks.
Field identification & locations
Look for a uniformly fine texture, high density, dark color, and tiny feldspar or pyroxene grains; a streak test is usually grayish. Common sources include volcanic regions, river gravels, and beaches.
