Basalt

Hardness of 6 on the Mohs scale, dark gray to black in color, aphanitic (fine-grained) texture, dull luster, and sometimes vesicular with gas cavities.

Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.

Used extensively in construction (crushed stone for road bases, concrete aggregate), railroad ballast, and sometimes in stonemasonry or countertops.

Basalt is the most common rock type in the Earth's oceanic crust and is also found abundantly on the Moon and Mars.

Easily identified by its dark, fine-grained appearance and heavy weight relative to its size. Commonly found in volcanic regions, oceanic islands, and flood basalt provinces worldwide.