igneous
Weathered iron-rich stone, likely basalt or ironstone
Probable basalt (mafic volcanic rock) with iron-oxide weathering; exact identification requires testing
AI-generated identification · may be incorrectDark reddish-brown, fine-grained, dull to weakly metallic surface with rounded water-worn form and vesicle-like pits. Typical basalt hardness is about 6 Mohs, with specific gravity ~2.8–3.1; the apparent cavity may be a weathered vesicle or impact pit.
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Physical properties
Dark reddish-brown, fine-grained, dull to weakly metallic surface with rounded water-worn form and vesicle-like pits. Typical basalt hardness is about 6 Mohs, with specific gravity ~2.8–3.1; the apparent cavity may be a weathered vesicle or impact pit.
Formation & geological history
Likely formed as rapidly cooled mafic lava, then altered and rounded by weathering and transport; commonly Cenozoic to Precambrian depending on source. Iron oxidation produced the rusty brown coating.
Uses & applications
Used as aggregate, roadstone, riprap, and occasionally as a decorative or lapidary material; this specimen has modest display value unless unusual provenance or composition is confirmed.
Geological facts
Basalt commonly contains plagioclase, pyroxene, and often olivine or magnetite. A magnet may detect magnetite; a fresh broken surface should be dark gray rather than uniformly rust-brown.
Field identification & locations
Common near volcanic terrains, riverbeds, glacial deposits, and iron-rich weathering zones. Test streak, magnetism, hardness, and reaction to dilute acid; a laboratory thin section or XRF would confirm the identification.
