igneous

Red Scoria

Scoria (Vesicular Basalt/Andesite)

Hardness: 5-6 Mohs. Color: Reddish-brown to dark red (due to iron oxidation). Luster: Dull to sub-vitreous. Structure: Highly vesicular (porous). Cleavage: None. Specific gravity: Variable but low (often sinks in water, unlike pumice).

Hardness: 5-6 Mohs
Color: Reddish-brown to dark red (due to iron oxidation)
Luster: Dull to sub-vitreous

Identified May 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich magma (mafic to intermediate) ejected during explosive volcanic eruptions. As the lava cools rapidly, the gases expand and escape, leaving behind a frozen 'foam' of bubbles or vesicles. Formed during the Cenozoic era in recent volcanic fields.

Uses & applications

Commonly used in landscaping (decorative 'lava rock'), gas grill bases for heat retention, high-temperature insulation, drainage rock, and in lightweight concrete as aggregate.

Geological facts

Scoria is often confused with pumice, but it is denser and has thicker vesicle walls. It is a key component of volcanic cones called 'cinder cones'. The red color is caused by the oxidation of iron-bearing minerals during or shortly after the eruption.

Field identification & locations

Identify in the field by its sponge-like appearance and light weight compared to solid rock. It is found in volcanic regions such as the American Southwest, Iceland, and Hawaii. It feels rough and abrasive to the touch.

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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