Most lead is obtained from galena, an ore consisting of a combination of lead and sulfur sometimes found in limestone. The lead is obtained by crushing the galena and then roasting it to drive off the sulfur. The roasted galena is mixed with coke and limestone and put into a furnace. Air is blown into the lower part of the furnace to make a draft for burning the coke, and the molten lead is drawn off from the bottom. The limestone helps to make the slag formed by the impurities run easily.
The lead thus obtained often contains small quantities of gold, silver, copper, and other metals, and requires further treatment to purify it. Sometimes enough silver is recovered to pay for the purification. The finished lead is cast into lumps called pigs. Much lead is obtained from scrap that is from old batteries and pipes which are melted down.