Basalts are magmatic rocks, created by the cooling of liquid magma on the earth's surface.

Because this cooling was relatively rapid, the minerals in the stone had little time to complete the crystallisation process.
This has resulted in a fine-grained appearance.

In general, basalts are non-porous, hard and capable of finishing in several different manners.
Their uses include flooring (indoors and outdoors), wall-covering, etc.