Tin

The simple oxide ore of tin, cassiterite (SnO2), accounts for virtually all the tin that has ever been recovered. It is noted for its high specific gravity (its heaviness), approximately three times the weight of a comparablysized piece of the granite with which it is normally associated. Where tin lodes have reached the surface, weathering and erosion over millions of years have broken up the vein structure and released the cassiterite which is stable and durable and resists rapid breakdown. It tends to lie on the surface as coarse eluvial material, often mixed with quartz. When washed into river valleys, it forms concentrated alluvial deposits of dark coloured pebbles and gravel.

Tin smelting in Cornwall was, on the whole, a more capital-intensive and lucrative business than mining and was controlled by a ‘ring’ or cartel of a few families. Money was often advanced to mines or miners, to be re-paid in tin. For the Bolitho family of Penzance this practice led to them becoming bankers. Thomas and William Bolitho founded The Mounts Bay Commercial Bank in 1807 in the count-house of their Chyandour Smelting House. The Consolidated Bank of Cornwall was taken over by Barclays Bank in 1905. The principal Cornish families engaged in tin smelting were the Daubuz, the Williams, the Harveys and the Bolithos.

The ownership of smelting houses, and of the smelting companies themselves, changed frequently throughout the nineteenth century as industrial families changed their alliances and strategies. A landmark technical improvement in Cornish tin smelting came in 1702. This was the introduction of the reverberatory furnace at Newham (Truro). This used coal instead of charcoal and the charge of tin was no longer mixed with (and contaminated by) the fuel but was reduced by the application of heat alone.
 

Weathering process of tin deposits. © HES.

By the nineteenth century, most tin smelting was conducted in reverberatory furnaces, although the larger and more important blowing houses remained until the mid century.Tin smelters within the region were initially concentrated close to the Stannary Towns and navigable rivers or harbours. Those in Cornwall tended to migrate from east to west as production shifted from tin-streaming to deep lode-mining. Most of these early important tin smelters were concentrated in Penzance, Hayle, Truro and the St Austell area. Later, when rail transport had developed (and coinage had been abolished) Redruth became an important centre for tin smelting.

Duchy of Cornwall coinage stamp. © Royal Cornwall Museum.


Uses of tin

For centuries, Cornish tin production was destined for The Worshipful Company of London Pewterers and gave rise to important medieval ports such as Truro. Coins were also minted: tin halfpennies and farthings were introduced by King James II (reigned 1685-1688). In all £10,000 worth of tin was purchased, and £65,000 worth of coins issued. Bronze (an alloy of copper and tin), once used in the production of cannon (before the development of large reliable iron castings) was also essential for precision instruments.

 

In 1789 a major new market was found for Cornish tin. The East India Company, which had a monopoly on all official “British” trade with China, began to buy around two thousand tons a year. This was consumed as tinfoil in religious ceremonies. Around half of this demand was met by Cornwall.

Tin-plated cans to preserve and transport food were invented by Peter Durand in 1810. During the early decades of the nineteenth century major growth in the tin-plate industry created a new and vibrant demand. Solder was an essential part of that industry and it also became a vital requirement of the electrical industry in the second half of the nineteenth century.

 

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