igneous

Basalt Riverstone

Basalt (Aphanitic Mafic Volcanic Rock)

Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when wet; Crystal Structure: Fine-grained (Aphanitic); Cleavage: None/Irregular; Specific Gravity: 2.8–3.0

Hardness: 6 (Mohs scale)
Color: Dark gray to black
Luster: Dull to sub-metallic when wet

Identified March 1, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when wet; Crystal Structure: Fine-grained (Aphanitic); Cleavage: None/Irregular; 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 Earth's surface. This specimen has been water-worn and smoothed in a river or coastal environment, likely during the Quaternary period.

Uses & applications

Commonly used as aggregate in construction, road base, and for high-quality decorative landscaping. Polished stones are used in hot stone massage therapy and minor jewelry/craft projects.

Geological facts

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

Field identification & locations

Identify by its heavy weight relative to size, dark uniform color, and lack of visible large crystals. Most common in volcanic regions and riverbeds downstream from volcanic plateaus.

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral