Basalt

Hardness: 6 on the Mohs scale, Color: Dark gray to black, Luster: Aphanitic (fine-grained) to glassy, Crystal structure: Microcrystalline, Cleavage: None, Specific Gravity: 2.8-3.0

Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface.

Commonly used in construction, crushed stone for road bases, concrete aggregate, and manufacturing of stone wool insulation.

Basalt is the most common rock type in the Earth's crust, making up most of the oceanic crust and forming massive geological formations like the Columbia River Basalt Group and the Giant's Causeway in Ireland.

Found worldwide in volcanic regions, oceanic islands, and continental flood basalt provinces. Identified by its dark color, heavy weight, and fine-grained texture.