smelting

“We hypothesize that the investment these populations made in producing iron metallurgy would have had significant environmental impact on local forest resources used for fuel. This remains to be demonstrated scientifically, but given the scale of smelting documented at Tugunbulak, it makes sense that there would have been consequential effects on the ecology of this highland landscape.”

The substance, called “copper concentrate”, is finely ground copper ore that has been treated to increase its copper content ahead of going on to be exported for smelting into refined copper.

Plumes of smoke from smelting factories fill the skyline, alongside some of the country's best-preserved world heritage sites from the Qing dynasty.

Certain industrial processes, such as metal smelting or combustion of manganese-containing fuels, can release airborne manganese which is later deposited in soils downwind.

Like the other big players, it has the latest equipment for gold smelting and refining, which it says is better for the environment and can guarantee the purity of its gold to extremely high levels.