The industrial mining landscape and economy, from 1700 to 1914
 

The nomination of the Cornwall and West Devon Mining Landscape for inclusion on the World heritage List is for the most universally significant era of Cornish mining between 1700 and 1914.

• the steady growth in Cornish and Devon tin production which was represented mostly by exploitation in depth and was based on underground lode mining (as opposed to tin streams). Small-scale tin-blowing was gradually replaced by larger-scale coal-fired reverberatory smelting.
   

• landmark technical advances in steam pumping which marked the formative period of the Industrial Revolution in Cornish mining. By the end of the eighteenth century deep mining was made possible by the development of this new technology.
   

• the mining of copper which experienced steady growth from the beginning of the eighteenth century. From 1750 to 1850 it was the most important mineral in the region. Cornish and West Devon output dominated the world’s copper markets.

A substantial amount of tin output in the region came from tin-streaming. Until the eighteenth century most tin came from these deposits. From the eighteenth century lode mining became dominant. There was a virtual absence of world competition in tin mining until the 1820s and the market remained dominated by Cornish tin until the 1870s. Periods of increased demand, such as the rapid rise of the tin-plate industry after 1800, strongly influenced the metal market price and hence production levels. The ability to increase production however depended upon the available mining technology of the time. The introduction of gunpowder for blasting and of reverberatory furnaces for smelting began a rising trend in production towards the end of the seventeenth century. From 1700 there began a steady improvement in the understanding of the nature of tin mineralisation and hence the ability to predict where tin deposits might lie. The development towards an industrial economy, with the ability to raise risk capital from investors, was a crucial factor that enabled expansion of the industry.
 

The improvement of steam pumping technology during the second half of the eighteenth century, and dramatic improvements to the Cornish engine from the 1820s enabled deeper mining and greater output. Cornish tin mines survived the threat of competition during the 1820s and 1840s from producers in the Far East. Following the 1866 copper crash, and the closure of a large percentage of Cornish copper mines, tin mines became the principal mines in the nominated Site. The 1870s marks the peak production period at a time when Malayan production was temporarily halted by internal political anarchy. From 1874 production declined as Australia and Malaya produced a large output from extensive shallow deposits of cheaply exploited ore that continued to be mined through the 1880s and 90s. The consequent drop in the tin price, coupled with a decline in investment and the irony of a shortage of miners due to emigration, caused production to continue to fall sharply. It was not until the second half of the twentieth century that there was a substantial recovery in output. This followed a programme of financial support targeted at the mining industry by the United Kingdom.
 

In the event, the readily-exploitable ores at Parys Mountain were worked out within two decades. Meanwhile the Cornish had responded to this threat to their mining economy through marked improvements in pumping technology and better working methods. During the early years of the nineteenth century Cornwall had once again become the pre-eminent copper ore producer in Britain, indeed, in the world; and was to remain so for several decades.
 

It was also used by other industries such as glass manufacture (as a decolouriser), in the production of lead-shot, in leather tanning, in wallpaper manufacture (to create green and yellow print), in pharmaceuticals, in agriculture for sheep dips and, from the 1870s, as a pesticide to control the Colorado beetle which devastated potato, tobacco and other crops in America during the late nineteenth century.

Calciners or ‘burning houses’ (furnaces) were an essential part of most eighteenth century Cornish tin mines whose ores contained arsenic and sulphur. These essential elements had to be ‘cleansed out’ by roasting as they proved deleterious to smelted tin. It was not until the nineteenth century however that demand arose, induced by technological advances, for the white arsenious oxide.

For some flagging copper mines, the working of arsenic provided several more years of profitable work and in some cases these ores became their principal output. Substantial works were established at the English Arsenic Company factory at Roseworthy, Gwithian and at Greenhill near Gunnislake, but the largest in the region was at Devon Great Consols, which at its peak produced 3,000 tons of refined arsenic a year. It was in the 1870s that a handful of mines in the Tamar Valley mining district were producing over half of the world’s arsenic; the works at Wheal Anna Maria (part of Devon Great Consols) covered 3.2 hectares and had over 6,850 cubic metres of arsenic flues.