igneous
Dark volcanic sand / basaltic sand
Basalt-derived lithic sand, chiefly plagioclase, pyroxene, and volcanic glass
AI-generated identification · may be incorrectBlack to dark gray, fine-grained, granular, and commonly weakly magnetic; individual grains are mostly submillimeter, with variable vitreous to dull luster. Basaltic grains typically have Mohs hardness about 5–6 and no visible cleavage as aggregate.
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Physical properties
Black to dark gray, fine-grained, granular, and commonly weakly magnetic; individual grains are mostly submillimeter, with variable vitreous to dull luster. Basaltic grains typically have Mohs hardness about 5–6 and no visible cleavage as aggregate.
Formation & geological history
Produced by weathering and erosion of mafic volcanic rocks, or by explosive volcanic activity; individual grains may range from recent to geologically ancient depending on source. The image appears to show loose natural sediment rather than a solid rock specimen.
Uses & applications
Used as landscaping material, filtration media, abrasive, aggregate, and occasionally in decorative jewelry or resin work. Common commercial value is low.
Geological facts
Basaltic sand is often enriched in iron- and magnesium-bearing minerals and may strongly attract a magnet if magnetite is abundant.
Field identification & locations
Common around volcanic islands, lava fields, beaches, and cinder cones, including Hawaii, Iceland, the Canary Islands, and parts of Japan. Identify it by its dark color, gritty texture, volcanic setting, and lack of cementation; a hand lens may reveal black pyroxene and pale plagioclase grains.
