igneous
Scoria (Basaltic)
Vesicular Basalt
Hardness: 5-6 (Mohs scale), Color: Dark brown to black, Luster: Dull/Earthy, Structure: Vesicular (full of air pockets/gas bubbles), Specific Gravity: 1.0-2.8 (often dense enough to sink, unlike pumice)
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark brown to black, Luster: Dull/Earthy, Structure: Vesicular (full of air pockets/gas bubbles), Specific Gravity: 1.0-2.8 (often dense enough to sink, unlike pumice)
Formation & geological history
Formed from the cooling of mafic lava rich in dissolved gases. As the lava erupts and pressure is released, gases expand creating bubbles (vesicles) that are frozen into the rock as it solidifies.
Uses & applications
Used in landscaping for 'lava rocks', as a drainage material in construction, as high-temperature insulation, and in some decorative gas fireplaces.
Geological facts
Scoria is often confused with pumice, but it is much denser and darker because it contains more iron and magnesium. It usually forms at the top of a lava flow or as a volcanic 'cinder' from explosive eruptions.
Field identification & locations
Identify in the field by its sponge-like appearance, dark color, and rough, abrasive texture. Commonly found in volcanic fields, especially near cinder cones and basaltic shield volcanoes.
