igneous
Iron-rich volcanic rock, possibly hematite-bearing basalt
Basalt with iron oxides; possible hematite/magnetite alteration
AI-generated identification · may be incorrectDark gray to black, fine-grained, irregularly vesicular and weathered, with reddish-brown iron-oxide patches and submetallic surfaces. Basalt is typically Mohs 5–6, with no visible cleavage and a specific gravity around 2.8–3.2; magnetite-rich areas may be weakly magnetic.
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Physical properties
Dark gray to black, fine-grained, irregularly vesicular and weathered, with reddish-brown iron-oxide patches and submetallic surfaces. Basalt is typically Mohs 5–6, with no visible cleavage and a specific gravity around 2.8–3.2; magnetite-rich areas may be weakly magnetic.
Formation & geological history
Likely formed as rapidly cooled lava, probably Cenozoic or older, then altered by oxidation and weathering. The image alone cannot establish a precise age or locality.
Uses & applications
Common basalt is used as aggregate, roadstone, riprap, and building stone; attractive polished pieces may be sold as curios, but this specimen has little jewelry value unless testing confirms a rarer material.
Geological facts
The reddish coloration commonly comes from hematite or limonite coating fractures and vesicles. A strong magnet response would suggest magnetite; a red-brown streak would support hematite.
Field identification & locations
Look for a fine-grained black matrix, abundant tiny cavities, and rusty oxidation. Common sources include volcanic regions worldwide; confirm with a streak test, magnet, hardness test, and ideally thin-section or XRF analysis.
