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
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Physical properties
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.
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.
