igneous

Basalt River Stone

Basalt (Aphanitic Mafic Igneous Rock)

Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull to sub-metallic, Crystal structure: Fine-grained/Aphanitic, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.8–3.0

Identified February 28, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull to sub-metallic, Crystal structure: Fine-grained/Aphanitic, 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 near the surface of a terrestrial planet or moon. This specific specimen has been polished smooth by water action in a river or coastal environment.

Uses & applications

Used extensively in construction as aggregate, road base, and concrete. Smooth specimens like this are used in landscape design, aquarium decor, and hot stone massage therapy.

Geological facts

Basalt is the most common rock on Earth's surface and also makes up most of the ocean floors and the lunar maria on the Moon.

Field identification & locations

Identify by its heavy weight (high density), dark color, and lack of visible large crystals. To distinguish from obsidian, check that it is opaque even on thin edges. Commonly found in volcanic regions and riverbeds.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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