igneous

Basalt River Stone

Basalt (Aphanitic Mafic Volcanic Rock)

Hardness: 5 to 6 on Mohs scale; Color: dark gray to black, turning brownish when weathered; Luster: dull to earthy; Crystal Structure: fine-grained (aphanitic) or glassy due to rapid cooling; Cleavage: none, usually breaks with a conchoidal fracture.

Hardness: 5 to 6 on Mohs scale
Color: dark gray to black, turning brownish when weathered
Luster: dull to earthy

Identified February 23, 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. This specific specimen shows rounding and smoothing characteristic of transport in a high-energy aquatic environment, such as a river or stream, over hundreds to thousands of years.

Uses & applications

Commonly used as aggregate in construction, road base, or railroad ballast. Polished versions are used for hot stone massage therapy and decorative landscaping.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.

Field identification & locations

Identified by its heavy weight (high density), dark color, and fine-grained texture with no visible crystals. Often found in volcanic regions or in riverbeds downstream from volcanic sources. Collectors value smooth, symmetrical 'worry stones' like this for tactile use.

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