igneous

Scoria

Scoria (Vesicular Basalt)

Hardness: 5-6 Mohs. Color: usually dark brown, black, or red. Luster: Dull/Sub-glassy. Structure: Highly vesicular (honeycombed with gas bubbles). Cleavage: None. Specific gravity: low (often sinks in water, unlike pumice).

Hardness: 5-6 Mohs
Color: usually dark brown, black, or red
Luster: Dull/Sub-glassy

Identified May 3, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the cooling of mafic magma (basaltic or andesitic) that is rich in dissolved gases. As the magma erupts, gases expand creating vesicles that are frozen into the rock as it solidifies.

Uses & applications

Used in landscaping as 'lava rock', high-temperature insulation, lightweight concrete aggregate, oil well drilling, and as a drainage medium in horticulture.

Geological facts

Scoria is often confused with pumice, but pumice is felsic (lighter color and weight), whereas scoria is mafic (darker and denser). Large deposits are commonly found near volcanic cinder cones.

Field identification & locations

Identify by its dark color, rough/sharp texture, and numerous distinctive holes (vesicles). Found globally in volcanic regions like Iceland, Hawaii, and Italy.

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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