igneous

Basalt River Stone

Basalt

Hardness: 6.0; Color: Dark grey to dull greenish-grey; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8 - 3.0

Hardness: 6
Color: Dark grey to dull greenish-grey
Luster: Dull/Earthy

Identified April 10, 2026More igneous →

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Physical properties

Hardness: 6.0; Color: Dark grey to dull greenish-grey; Luster: Dull/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 at or near the Earth's surface. Extrusive igneous rock. This specific specimen has been shaped by fluvial (river) erosion.

Uses & applications

Commonly used as aggregate in construction, road base, and for architectural uses like stone walls or decorative landscaping. Smooth ones are often used in hot stone massage therapy.

Geological facts

Basalt is the most common rock type 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 in the field by its heavy weight, fine-grained texture (no visible crystals), and rounded shape if found near water. Often lacks the layering found in sedimentary rocks.

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