igneous

Basalt River Stone

Basaltic Igneous Rock

Hardness: 6 on Mohs scale; Color: Dark grey to dull black; Luster: Dull or earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8 to 3.0. This specimen shows a smooth, water-worn texture.

Hardness: 6 on Mohs scale
Color: Dark grey to dull black
Luster: Dull or earthy

Identified May 4, 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 very near the Earth's surface. This particular specimen has been naturally tumbled and smoothed by river or coastal water movement.Basalt is found throughout Earth's history, especially in oceanic crust.

Uses & applications

Basalt is used extensively in construction as aggregate, for road base, and in concrete. River-worn basalt is popular in landscaping, aquarium decor, and as massage stones.

Geological facts

Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon (the dark lunar Maria) and Mars.

Field identification & locations

Identify by its heavy weight (high density), dark color, and fine-grained texture. It often shows smooth, rounded edges if found in water environments. Found globally in volcanic regions and riverbeds downstream from volcanic sources.

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