Igneous

Vesicular Basalt (Scoria)

Extrusive Mafic Volcanic Rock (FeO-SiO2-MgO)

Hardness: 5-6 Mohs; Color: Dark grey, black, or reddish-brown with olive tones (indicative of olivine); Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0; Texture: Vesicular (pitted with gas bubbles).

Hardness: 5-6 Mohs
Luster: Dull to earthy

Identified March 30, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The pits (vesicles) are created by gas bubbles that were trapped as the lava solidified. These are typically associated with Cenozoic to Holocene volcanic activity.

Uses & applications

Commonly used in landscaping (lava rocks), as a high-friction road aggregate, in the production of stone wool insulation, and occasionally as a lightweight abrasive in industrial applications.

Geological facts

Basalt is the most common rock on the Earth's surface, making up most of the ocean floor. The olive-green tint on this specific specimen likely indicates a high concentration of the mineral olivine, which is the primary component of the Earth's upper mantle.

Field identification & locations

Identify in the field by its dark color, heavy weight (relative to size, unless extremely vesicular like pumice), and distinctive 'vesicles' or holes. It is commonly found in volcanic fields like those in Iceland, Hawaii, and the Pacific Northwest, USA.

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