Basalt

Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull luster, specific gravity around 2.8-3.0.

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 in construction, aggregate for roads, making stone wool insulation, and manufacturing tiles.

Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forms famous formations like the Giant's Causeway in Northern Ireland.

Easily identified by its dark, dense, fine-grained appearance, often found in volcanic regions, oceanic crust, and basaltic lava flows.