Coal and charcoal in medieval metallurgy

Sep 2007
N. Va.
charcoal was the preferred fuel for smelting but coal became more popular in the 18th century as the process of making coke from coal became more refined. As well, the forests of Europe were becoming rapidly depleted b/c of the dependence on charcoal.

I was wondering if anyone had information on the usage of coke or coal in the smelting process prior to the 18th century in Europe (or elsewhere for that matter).

I've visited a number of "history of coal" sites on the Web and pre-18th century usage is practically nonexistent.