igneous

Lava Rock (Scoria)

Scoria (Vesicular Basalt)

Hardness: 5-6 Mohs. Color: Dark brown, black, or reddish-brown. Luster: Dull/earthy to sub-metallic. Crystal structure: Aphanitic (fine-grained) with many vesicles (holes). Specific gravity: 0.8–2.1 (relatively low due to air pockets).

Hardness: 5-6 Mohs
Color: Dark brown, black, or reddish-brown
Luster: Dull/earthy to sub-metallic

Identified February 7, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of gas-rich mafic magma (basaltic) extruded from a volcano. The gas bubbles are trapped as the lava solidifies, creating the 'vesicular' texture. Most common in recent Quaternary volcanic fields but found throughout geological history.

Uses & applications

Extensively used in landscaping (lava rock), high-temperature insulation, concrete aggregate, gas grills, and drainage systems. Occasionally used for aquarium decor and stone-washing textiles like jeans.

Geological facts

Scoria is often confused with pumice, but scoria is denser, has larger vesicles, and generally sinks in water, whereas pumice floats. It is a major component of cinder cones around the world.

Field identification & locations

Identify in the field by its very high porosity, dark color, and sharp, abrasive surface. Common in volcanic regions like Hawaii, Iceland, and the American Southwest. Collectors should look for unique aerodynamic shapes (volcanic bombs) or interesting color variations.

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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