igneous

Basalt

Basalt (Mafic volcanic rock)

Hardness: 6 (Mohs); Color: dark gray, black, or dark green; Luster: dull to earthy; Texture: aphanitic (fine-grained) to porphyritic; Crystal structure: tiny crystals of plagioclase feldspar and pyroxene.

Hardness: 6 (Mohs)
Color: dark gray, black, or dark green
Luster: dull to earthy

Identified January 15, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. This specimen shows signs of anthropogenic modification (shaping) into a projectile point.

Uses & applications

Primarily used as an aggregate in construction projects, for road base, and concrete. This specific shaped specimen has archaeological and historical value as a lithic tool.

Geological facts

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

Field identification & locations

Identified by its dark, heavy, and fine-grained appearance. In the field, look for volcanic provinces or basaltic plateaus. To identify as a tool, look for percussion bulb scars and flaking patterns along the edges.

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