igneous

Basalt (Vesicular)

Basalt (Mafic volcanic rock)

Hardness: 5-6 Mohs. Color: Dark gray to black, often weathering to brown or olive. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) with small pits or cavities (vesicles). Specific Gravity: 2.8–3.0.

Hardness: 5-6 Mohs
Color: Dark gray to black, often weathering to brown or olive
Luster: Dull/Earthy

Identified May 24, 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 specimen appears scoriaceous or vesicular, which occurs when gases escape during cooling.

Uses & applications

Used primarily as crushed stone for road base, concrete aggregate, railroad ballast, and sometimes as 'lava rock' for landscaping or filtration.

Geological facts

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

Field identification & locations

Identify by its dark color, heavy weight (density), and lack of visible large crystal grains. Common in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.

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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