igneous

Scoria (Vesicular Basalt)

Scoria (Extrusive Igneous Rock)

Hardness: 5-6 (Mohs scale); Color: Dark brown, black, or reddish-brown; Luster: Dull/Earthy; Crystal Structure: Aphanitic (fine-grained) with large vesicles (gas bubbles); Cleavage: None; Specific Gravity: 0.8 - 2.1 (relatively light due to air pockets).

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

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of basaltic or andesitic lava containing high amounts of dissolved gases. As the magma erupts, gases expand and escape, leaving behind a 'frozen' foam of holes. Geologically common from the Cenozoic era to the present in volcanic fields.

Uses & applications

Commonly used in landscaping (lava rock), high-temperature insulation, lightweight concrete aggregate, traction on snow-covered roads, and gas grill heat retention.

Geological facts

Scoria is often confused with pumice, but scoria is more dense and sinks in water, whereas pumice typically floats. It is a primary component of cinder cones, which are the simplest type of volcano.

Field identification & locations

Identify by its 'Swiss cheese' appearance, rough/abrasive texture, and dark color. It is commonly found around volcanic vents and cinder cones. In the field, look for a lightweight, jagged rock that feels like sandpaper.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral