Phytokarst is a distinctive landform resulting from a curious type of biologic erosion. Filamentous algae bore their way into limestone to produce black-coated, jagged pinnacles marked by delicate, lacy dissection that lacks any gravitational orientation. Ordinary rainfall-produced karst and littoral karst are characterized by flat-bottomed pans and vertically oriented flutes, thus differing from phytokarst. Algae attack by dissolving calcite preferentially to dolomite.