Basalt

Basalt is a special type of block that can only be created, but not with a crafting surface. It was introduced in version 1.1.

Appearance
Basalt is generally black liberally covered with white to gray speckles. In version 1.2, it changed to become shinier and to have a unique texture when painted.

Where Found
Unlike other blocks, basalt is not spawned as part of a world. Instead, it is created when water is placed on top of magma near the center of the world. It must then be mined. This was made more difficult in version 1.5 with the addition of death.

Note that water occurring naturally (i.e. as part of world generation) on top of magma does not form basalt unless disturbed.

Crafting
Basalt can be crafted into columns and stairs at a builder's bench.

Uses
Basalt is useful in construction.