Anaconda smelter, Montana. Anaconda Copper Mining Company. Concentrate, known as calcine, is moved red-hot from the roasting furnaces to the reverberatory smelting furnaces. In the reverberatory furnace the second major elimination of impurities is accomplished; in this furnace two products are produced; one, the matte, which contains the precious metals and copper; the other, the slag, which contains impurities which float on the surface. The slag is poured off and sent to the dump