igneous

Basalt River Stone

Basalt

Hardness: 6 (Mohs scale); Color: Black or dark grey; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None/Conchoidal fracture; Specific gravity: 2.8–3.0

Hardness: 6 (Mohs scale)
Color: Black or dark grey
Luster: Dull to sub-vitreous

Identified May 13, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale); Color: Black or dark grey; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None/Conchoidal fracture; Specific gravity: 2.8–3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been Rounded and polished by water erosion in a river or coastal environment.

Uses & applications

Commonly used in landscaping, as massage stones in spas, in construction as crushed aggregate, and as decorative pieces in aquarium or garden design.

Geological facts

Basalt is the most common rock on Earth's surface and also makes up the majority of the ocean floor. It is found on other planetary bodies like the Moon, Mars, and Venus.

Field identification & locations

Identified by its dark color, heavy weight for its size, and absence of visible large crystals to the naked eye. Commonly found on beaches, riverbeds, and in volcanic regions.

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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