Arsenic is a chemical element which can be found in many minerals, usually combined with metals or sulphur. It was a valuable by-product of tin and copper mining in Cornwall and was widely used in a variety of industries. But why was it so important? And how did they extract it?
What was arsenic used for?
In the 1870s a handful of mines in Cornwall produced over half the world’s arsenic.
The principal market for arsenic was the expanding Lancashire cotton industry, which used it in pigments and dyes. Arsenic was also used by other industries such as glass manufacture (as a decolouriser), in the production of lead-shot, in leather tanning and in wallpaper manufacture (to create green and yellow print).
Despite its toxicity, it had a number of beneficial medicinal uses so was also sought after by the burgeoning pharmaceutical industry. It was also widely used in agriculture for sheep dips. From the 1870s, arsenic was used as a pesticide to control the Colorado beetle which devastated potato, tobacco and other crops in America during the late 19th century.
Using calciners to extract arsenic
Calciners were an essential part of most 19th century Cornish tin mines whose ores contained contaminating arsenic and sulphur. These had to be removed by roasting as they made the smelted tin brittle and reduced its value.
Arsenic is highly toxic, and surface workers risked arsenic poisoning through continued exposure.
Brunton calciners became the most commonly used type and these were often tended by women or girls. The contaminated ores were fed into the furnace through the hopper located above its rotating hearth.
How arsenic helped boost the mining industry
Arsenic helped control the Colorado beetle, which devastated potato crops and tobacco across America.
For some flagging copper mines, extracting arsenic provided several more years of profitable work – and in some cases became their principal output. The English Arsenic Company established substantial works 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. In the 1870s a handful of mines in Cornwall produced over half the world’s arsenic. Arsenic is highly toxic, and surface workers risked arsenic poisoning through continued exposure.