igneous
Weathered basalt pebble
Basalt, a fine-grained mafic volcanic rock; likely containing plagioclase, pyroxene, and iron-titanium oxides
AI-generated identification · may be incorrectHardness about 5–6 Mohs; pale gray to cream weathering rind with dark gray-black patches, dull to faintly earthy luster, and massive fine-grained texture. No obvious cleavage or visible crystals; rounded shape indicates water abrasion.
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Physical properties
Hardness about 5–6 Mohs; pale gray to cream weathering rind with dark gray-black patches, dull to faintly earthy luster, and massive fine-grained texture. No obvious cleavage or visible crystals; rounded shape indicates water abrasion.
Formation & geological history
Formed when basaltic lava rapidly cooled at or near Earth’s surface, then weathered and rounded in a river, beach, or glacial environment. Its exact geological age cannot be determined from the image.
Uses & applications
Commonly used as aggregate, road stone, riprap, and landscaping material; this rounded specimen has mainly educational or decorative value rather than gem value.
Geological facts
Basalt is the most abundant volcanic rock on oceanic crust and commonly weathers to brown, red, or cream surfaces. The dark areas may represent fresher basalt, iron-oxide staining, or weathered mafic minerals.
Field identification & locations
Identify by its heavy, fine-grained texture, dark streak or interior, lack of visible quartz, and resistance to scratching by a steel blade. Common worldwide, especially in volcanic regions, streambeds, beaches, and glacial deposits.
