Basalt

Hardness of 6 on the Mohs scale, typically dark gray to black in color, dull to sub-with a fine-grained aphanitic texture, specific gravity ranges from 2.8 to 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, often originating from volcanic hotspots or divergent plate boundaries.

Widely used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in manufacturing stone wool insulation and occasionally for decorative stone tiles.

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

Easily recognized in the field by its very dark, fine-grained groundmass and heavy weight relative to its size; common globally in volcanic regions such as Iceland, Hawaii, and oceanic spreading centers.