This technique gives the pot a unique textured surface.  A pot is traditionally thrown, then dried clay is ground to a coarse meal and applied to the outer surface of the wet pot.  As the pot dries, the ground clay adheres to the surface.  Next, the pot is bisque fired and stained with several zinc oxide stains.  The result is a pot that looks as though it was carved from a piece of lava rock.  The pot can be left unglazed or sprayed with a thin clear coat giving is a shiny, polished look.