igneous

Scoria (Lava Rock)

Scoria (Mafic volcanic rock)

Hardness: 5-6 (Mohs scale); Color: Dark red, brown, or black; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: 2.0-3.0 (lightweight but usually sinks in water).

Hardness: 5-6 (Mohs scale)
Color: Dark red, brown, or black
Luster: Dull/Earthy

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed from basaltic or andesitic magma. As gas escapes during an explosive volcanic eruption, the molten rock cools quickly, trapping bubbles of gas (vesicles). It is often found in volcanic cinder cones and lava flows.

Uses & applications

Commonly used in landscaping (drainage and decoration), gas grills (lava rocks), high-temperature insulation, and as a lightweight aggregate in concrete and road construction.

Geological facts

Scoria is different from pumice because it has larger vesicles and thicker cell walls, making it denser. While pumice usually floats, most scoria will sink. Red scoria is often used as 'lava rock' for decorative gardens.

Field identification & locations

Identify by its 'Swiss cheese' appearance, rough/sharp edges, and reddish-brown to black color. It is extremely common in volcanic regions like the American Southwest, Iceland, 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