Dirt is the layer of soil above Gravel and underneath Topsoil. It is brown in color and, like Topsoil, drops regular Dirt when mined. This block exists on all moons, regardless of the moons world settings.
Dirt is commonly found immediately below the Topsoil blocks or Sand and above Sravel, and is about three blocks thick. Dirt can also occasionally be found at the surface, replacing the Topsoil, and also exist as random clusters in Rock