What materials were used in ancient furnaces for smelting copper and iron?

In ancient China, pig iron was mainly smelted by shaft furnace, which was developed from copper smelting shaft furnace. Shaft furnace ironmaking is an economical and effective ironmaking method. Charging from the top and blowing from the bottom lead to the relative movement of burden falling and gas rising. The high-temperature gas produced by combustion rises through the material layer and transfers heat to the charge. The carbon monoxide contained in it also reduces iron oxide. In this way, the thermal energy and chemical energy of combustion are fully utilized at the same time. The lower burden gradually decreases or even melts, and the upper burden gradually decreases.