igneous

Red Scoria (Lava Rock)

Scoria (Extrusive Igneous Rock / Mafic composition)

Vesicular texture (pitted with holes); Hardness: 5-6 (Mohs); Color: Reddish-brown to dark red; Luster: Dull/Earthy; Crystal structure: Glassy/Aphanitic; Specific gravity: 0.8-2.6 (though often floats briefly in water due to trapped air).

Hardness: 5-6 (Mohs)
Color: Reddish-brown to dark red
Luster: Dull/Earthy

Identified March 9, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich basaltic or andesitic magma. As the lava is ejected during a volcanic eruption, it cools rapidly while gas bubbles are still trapped inside, creating the vesicular holes. Commonly found in cinder cones and volcanic fields produced during the Holocene to Pleistocene epochs.

Uses & applications

Used extensively in landscaping, gas grill briquettes, drainage stone, high-temperature insulation, and lightweight concrete aggregates. In some cases, it is used for foot pumice or abrasive cleaning.

Geological facts

Red scoria gets its color from the oxidation of iron within the lava while it is still hot. It is the primary component of many cinder cone volcanoes, such as those found in the American Southwest or Iceland.

Field identification & locations

Identify in the field by its very lightweight, 'sponge-like' appearance and sharp, jagged edges. It is often found in volcanic regions like Arizona, Hawaii, and Italy. Collectors look for pieces with unique cooling patterns or embedded crystals like olivine.

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

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral