igneous
Weathered volcanic rock, likely andesite or basalt
Fine-grained mafic to intermediate volcanic rock; commonly plagioclase, pyroxene, and possible iron oxides
AI-generated identification · may be incorrectHardness approximately 5.5–6.5 Mohs; gray-green to brown with rusty oxidation patches, dull to faintly lusterous, dense and fine-grained. The rounded shape and small cavities suggest stream abrasion and minor vesicular texture.
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Physical properties
Hardness approximately 5.5–6.5 Mohs; gray-green to brown with rusty oxidation patches, dull to faintly lusterous, dense and fine-grained. The rounded shape and small cavities suggest stream abrasion and minor vesicular texture.
Formation & geological history
Formed when lava cooled rapidly at or near Earth’s surface, probably during the Cenozoic or older; exact age and composition require thin-section or geochemical testing. Surface weathering produced the brown iron-oxide staining.
Uses & applications
Used locally as aggregate, riprap, road material, and landscaping stone; this ordinary rounded specimen has little jewelry or commercial value.
Geological facts
Its greenish coloration may reflect chlorite or other alteration minerals, while reddish-brown areas are likely limonite or hematite. The image does not show diagnostic crystals or layering sufficient for a more specific identification.
Field identification & locations
Common in volcanic terrains and streambeds worldwide; test for a glassy or fine-grained texture, substantial density, and lack of acid reaction. A streak, magnetism test, and fresh broken surface would improve identification.
