igneous
Vesicular volcanic rock, likely scoria
Scoria; composition commonly basaltic to andesitic, rich in plagioclase and pyroxene
AI-generated identification · may be incorrectDark reddish-brown, strongly vesicular, rough and dull with small gray mineral grains; typically Mohs 5–6, no obvious cleavage, and specific gravity about 2.0–2.8. The rusty color reflects oxidation of iron-bearing minerals.
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Physical properties
Dark reddish-brown, strongly vesicular, rough and dull with small gray mineral grains; typically Mohs 5–6, no obvious cleavage, and specific gravity about 2.0–2.8. The rusty color reflects oxidation of iron-bearing minerals.
Formation & geological history
Forms when gas-rich mafic lava cools rapidly at or near a volcanic vent, trapping bubbles; it is generally geologically young, ranging from recent eruptions to older volcanic deposits. Common sources include cinder cones, lava flows, and volcanic fields.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasives, and occasionally in decorative rock collections; generally not a jewelry material.
Geological facts
Scoria is denser and darker than pumice, which can float because of its abundant interconnected pores. The specimen’s rounded shape may reflect weathering or tumbling rather than its original volcanic form.
Field identification & locations
Identify it by abundant irregular holes, reddish-black color, low density, and a gritty volcanic texture; common worldwide near basaltic volcanoes, including Hawaii, Iceland, Mexico, and the western United States. Exact identification would benefit from a fresh surface and density test.
