High temperatures would be needed in order to smelt tin presumably so I am puzzled by this statement, from a historian called Craig Weatherhill, regarding the Cornish tin industry
From the Bronze Age through to the Tudor period, mining in Cornwall needed very little fuel (and we produced a large amount of copper and iron, too).
Our view is that deforestation which was a widespread practice is particularly marked in tin-working regions due to the fuel requirement. However Mr Weatherhill also thinks that the entire landscape was in effect sculpted by it [mining]:
It took two main forms: lode-back workings, digging down into an outcropping lode, producing trench-like excavations; and streaming. Alluvial and elluvial. These were quite elaborate, and changed the contours of many valleys. Streaming didn't involve a man with a sieve - there was much more to it. There isn't a valley in West Cornwall that hasn't been streamed, and a steep scarp on either side, well back from the watercourse, is a giveaway. In these, particularly the elluvial type, artificially created water power was vital.