Manufacturing Industries - Ore Processing and Smelting

The large number of mines, extracting various types of metalliferous ores, which operated in and around the Tamar Valley between the 12th and 20th centuries, needed to process these ores to render them saleable. From the earliest times, the sorting and breaking of these ores was usually carried out by hand on dressing floors close to the shafts or adit entrances out of which they were brought to surface. Large piles of waste rock and unwanted minerals such as iron or arsenic pyrites (Arsenic was only considered important after the 1860s) are typically found near a dressing floor, usually broken up quite small.

Dressing the crushed material to separate the copper and tin ore from the waste rock was traditionally carried out using water in wooden boxes known as buddles, in conjunction with settling pits. From the mid-19th century, technology improved: increasingly complicated machinery being employed to extract as much valuable material from the crushed ore.

Smelting - that is: melting the dressed ore, running off impurities in the form of slag, and casting the finished metal into ingots, was carried out in various places, depending on the date and the complexity of the ore.

Tin was smelted locally with charcoal until the early 19th century when large-scale refineries were set up in Cornwall and especially South Wales, where coal was plentifully available. The copper ores found in the district are complex sulphides, needing a high temperature to extract the copper. It is not known whether copper smelting was attempted locally before the early 18th century, but at this time several smelters were set up in South Wales and the Forest of Dean, where coal was freely available.