Basalt

Hardness of 6 on Mohs scale, dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity of 2.8-3.0

Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface, often from volcanic eruptions or oceanic crust formation

Used extensively in construction as crushed aggregate for roads, railroad ballast, concrete production, and in the manufacturing of rock wool insulation

Basalt is the most common rock type in the Earth's crust underlying the world's oceans and is also the primary volcanic rock found on the Moon and Mars

Easily identified by its dark, fine-grained appearance, heavy weight, and dense composition, commonly found in volcanic regions and oceanic islands worldwide