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)

Identified April 11, 2026More igneous →

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Physical properties

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.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous