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Basalt

Basalt is an aphanitic extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a rocky planet or moon.

Colors It Comes In - dark grey to black

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Fracture Pattern - (1) colonnade, (2) entablature, (3) horizontal fractures near flow tops, and (4) inflation

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Shape - colonnade

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Luster - dull

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Texture - fine-grained, aphanitic

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Where It Can Be Found - Basalt is one of the most popular rock types, covering more than 70% of the Earth's surface. It forms in many places, including mid-ocean ridges, island arcs, ocean islands, rifting valleys, and back-arc basins.

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Hardness On The Mohs Scale - 5 To 6 Out Of 10

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