igneous
Scoria (vesicular basalt)
Vesicular basalt; chiefly plagioclase, pyroxene, and iron-rich glass/oxides
AI-generated identification · may be incorrectDark reddish-brown, highly vesicular, dull to slightly glassy luster, and very low apparent density; hardness about 5–6 Mohs. The irregular holes are gas bubbles, and the red color commonly reflects oxidation of iron minerals.
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Physical properties
Dark reddish-brown, highly vesicular, dull to slightly glassy luster, and very low apparent density; hardness about 5–6 Mohs. The irregular holes are gas bubbles, and the red color commonly reflects oxidation of iron minerals.
Formation & geological history
An extrusive volcanic rock formed when basaltic lava cooled rapidly while releasing dissolved gases; oxidation may occur during or after eruption. It is generally geologically young, ranging from recent volcanic material to ancient flows.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and occasionally decorative rock; it has little gemstone value.
Geological facts
Scoria is typically denser and darker than pumice, with thicker vesicle walls and abundant iron-rich minerals. Its vesicles may be partly filled by later minerals such as zeolites, calcite, or quartz.
Field identification & locations
Identify it by its rusty red-black color, abundant interconnected cavities, rough texture, and volcanic appearance; it commonly occurs around cinder cones, lava flows, and basaltic volcanoes worldwide. This specimen could also be vesicular basalt rather than true scoria if unusually dense.
