igneous
Weathered vesicular volcanic rock, likely scoria
Scoria (vesicular basalt), composed chiefly of plagioclase, pyroxene, and iron-rich glass
AI-generated identification · may be incorrectTypically dark gray to reddish-brown, porous, and dull to slightly glassy, with abundant gas vesicles; Mohs hardness about 5–6, no consistent cleavage, and specific gravity commonly 2.0–2.8. The orange-brown color indicates oxidation of iron-bearing minerals, while pale spots may be weathered feldspar or secondary mine…
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Physical properties
Typically dark gray to reddish-brown, porous, and dull to slightly glassy, with abundant gas vesicles; Mohs hardness about 5–6, no consistent cleavage, and specific gravity commonly 2.0–2.8. The orange-brown color indicates oxidation of iron-bearing minerals, while pale spots may be weathered feldspar or secondary minerals.
Formation & geological history
Forms when gas-rich basaltic lava erupts and rapidly cools, trapping bubbles; likely Cenozoic or younger, though age cannot be determined from an image. Common in cinder cones, lava flows, and volcanic fields.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasive, and sometimes in decorative rock collections; generally low gem value.
Geological facts
Scoria is denser and darker than pumice and usually has thicker, more interconnected walls around its vesicles. The specimen appears strongly weathered and may contain secondary mineral crusts.
Field identification & locations
Identify it by its reddish-black color, rough porous texture, and basaltic weight; common worldwide near basaltic volcanoes, including the western United States, Iceland, Italy, and Japan. A chemical or thin-section test would be needed for certainty.
