igneous

Basalt River Stone

Basalt

Hardness: 6-7 (Mohs scale); Color: Dark grey to black, weathering to brown; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0

Hardness: 6-7 (Mohs scale)
Color: Dark grey to black, weathering to brown
Luster: Dull to earthy

Identified May 26, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Dark grey to black, weathering to brown; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava. This specific specimen has been rounded and smoothed by water erosion (alluvial action) over thousands of years.

Uses & applications

Used widely in construction (crushed stone), decorative landscaping, massage therapy (hot stones), and as an abrasive in industrial applications.

Geological facts

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

Field identification & locations

Identify by its heavy weight (density), dark color, and fine-grained texture. Commonly found in riverbeds near volcanic regions or as decorative landscape gravel.

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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