igneous
Vesicular basalt (possibly weathered scoria)
Basalt; chiefly plagioclase feldspar, pyroxene, and iron-rich minerals
AI-generated identification · may be incorrectTypically dark gray to reddish-brown with abundant rounded gas vesicles, dull to slightly earthy luster, and very fine-grained texture; hardness about 5–6 Mohs, no visible cleavage, and specific gravity roughly 2.7–3.0. The reddish color likely reflects oxidation and weathering.
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Physical properties
Typically dark gray to reddish-brown with abundant rounded gas vesicles, dull to slightly earthy luster, and very fine-grained texture; hardness about 5–6 Mohs, no visible cleavage, and specific gravity roughly 2.7–3.0. The reddish color likely reflects oxidation and weathering.
Formation & geological history
An extrusive volcanic rock formed when gas-rich basaltic lava cooled rapidly at or near Earth’s surface; the exact age cannot be determined from the image and may range from recent to ancient. Common in lava flows, volcanic fields, and shoreline environments.
Uses & applications
Used as aggregate, road material, riprap, landscaping stone, and occasionally as a decorative or lapidary specimen; this heavily weathered piece has limited commercial value.
Geological facts
Its holes are vesicles—bubbles trapped in cooling lava—not sedimentary pores or fossils. Vesicle abundance and reddish oxidation are characteristic of scoria-like basalt, although the specimen appears relatively dense.
Field identification & locations
Identify it by its lightweight-to-moderate density, tough fine-grained texture, lack of obvious mineral crystals, and numerous irregular cavities; a streak test is usually gray to brown. Common worldwide in volcanic regions, including Hawaii, Iceland, the western United States, and oceanic islands.
