The use of raw dolomite "famming in" bottom for basic open hearth furnace has not been consideyed seriously hitherto. Provided that the surface is sintered to a certain extent, it is just as good as the dolomite clinker bottom. It withstands well the violent oxidizing boil in refining. It is not necessary to take heed to slaking properties for the cooling off of furnace for a long period. It's structure consists of following as:-periclase, olivineforsterite, diopsite and others.