NPT 170101 12" x 24" Greyon Honed Basalt Tile - Basalt is the most common volcanic rock in the Earth’s crust. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It is a good heat insulator. Basalt has been used in construction as building blocks or for flooring and paving in public places. Recently has become more popular as a decorative item in contemporary architecture.