Peat bogs reveal only sporadic exploitation of South-west England’s tin deposits in the Bronze Age, suggesting only limited tin mining and bronze production in the area at that time.
From Planet Earth Online:
Britain was a major source of tin in the ancient world but details of how this important commodity was exploited were sketchy at best – until Andy Meharg and colleagues Kevin Edwards and Ed Schofield got stuck into two West Country peat bogs.
Tin has played an important role in the development of human society. Either on its own or mixed with copper to form bronze, it had a place in everything from coins and jewellery to armour and weapons. But unlike copper, tin deposits are extremely rare, and ancient Mediterranean cultures (from the Bronze Age through to Roman times) had to look to the remote Atlantic fringes of Europe for their closest supplies.
South-west Britain was home to the largest European tin deposits, and this mineral wealth must have been a significant source of economic and cultural contact between Britain and mainland Europe. But there is not much evidence, archaeological or historical, for how the tin trade developed.
Around 440BC, the Greek historian Herodotus wrote about tin sources in the ancient world: ‘I cannot speak with certainty, however, about the marginal regions which lie toward the west, in Europe...Nor am I certain of the existence of the Cassiterides Islands, from which we get our tin.’ Pytheas of Massalia (modern Marseilles), who is credited with being the first person to circumnavigate Britain around 300BC, also talked of a tin-bearing island named Mictus within six days’ sail of Britain.
Cornwall, particularly St Michael’s Mount, has long been associated with the ‘tin islands’ – the Cassiterides – to which Herodotus referred, but it’s not much to go on.
In an attempt to add to the body of evidence, myself and colleagues at the University of Aberdeen looked to the peat bogs of the south-west. These bogs have been soaking up atmospheric pollution for centuries and we hoped that pollution would include traces of tin released into the atmosphere from mining and tinworking. The sites we chose – Tor Royal on Dartmoor and Dozmary Pool on Bodmin Moor – are themselves better known as the location for Sherlock Holmes’ encounter with the Hound of the Baskervilles, and the place where King Arthur deposited Excalibur, respectively. More pertinent to our study, though, is that both lie undisturbed in the middle of an ancient tin-mining region, and both are ombrotrophic – they get all their water from rainfall rather than from springs or streams. This is important because it means any minerals they contain must have been deposited from the atmosphere rather than carried from surrounding rocks or soils.
Our approach was based on the fact that minute particles of tin are released when ore is crushed and smelted, and these eventually fall back to the ground or are washed out of the atmosphere by rain. Assuming these particles had accumulated and lain undisturbed in the bogs, analysing the amount of tin at different depths would give us a sequence of tin exploitation, with greater concentrations representing periods of more intense mining and smelting. And because the bogs are made up of organic material, we could radiocarbon date the layers associated with different phases of tin deposition to find out when they had occurred.
Our specialised equipment enabled us to core 4m down through the peat, so we were able to work out a chronology of tin deposition and, by analogy, of tin mining and smelting, going back thousands of years.
This chronology adds so much detail to what we know about this period that it will allow us to rewrite the story of ancient Britain’s trade links with Europe.
Analysis of the Himmelsscheibe, a bronze disk found near Leipzig, Germany, which is inlayed with a gold map of the heavens and dates to around 1600BC, indicates that it contains tin ores from south-west Britain. So British tin was undoubtedly traded to some extent during the Bronze Age, but our findings suggest that production was low.
The cores showed that, at most, there was only sporadic atmospheric deposition of tin into the peat during the Bronze Age, between around 2500 and 800BC, and this pattern continued until early Roman colonisation, around AD100. This confirms what we had already gleaned from archaeological and fragmentary documentary evidence; that there may have been only limited tin mining and bronze production in south-west Britain over this period.
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