Harrow and Hillingdon Geological Society

Previous Meetings

Dr Paul Craddock

The British Museum

The development of mining dates from prehistoric periods and native copper was being extracted as ore bodies in the Middle East 10,000 years ago. There is no evidence for the use of gold in either the Neolithic or Palaeolithic periods. The copper was used just for trinkets such as beads and jewellery but not tools, and this practice remained for several thousand years.

Smelting seems to have developed about 8,000 years ago and there is evidence for it in the earliest mines in Rumania.

Indications for possible mineral deposits are associated with the presence of quartz dykes. These are formed in fissures within the metamorphic rocks and are associated with a wide variety of metal silicates. These deposits, e.g. iron, become weathered and degraded and are precipitated into the lower strata often as layers of sulphide deposits.

The technique of looking for dykes is fine in areas around the Mediterranean Sea and in the Middle East but within the temperate zones where there is a lot of vegetation; quartz dykes are often not visible. In addition the gossans, or iron rich caps on the dykes in the arid regions, have been removed further north by glaciation during the ice ages. Minerals and quartz also occur in stream beds and on cliff faces and local vegetation might hint at their presence. Some plants are resistant to the effects of heavy metals such as lead and can indicate possible deposits. Today, aerial photography is used a lot to identify sites.

Hard Rock Mining

In areas of Britain, China and Columbia etc, rocks were softened by the use of fire thereby allowing miners to remove the minerals with the use of flint tools. It was a time consuming business. It required a great deal of wood as the heat penetrated the stone face very slowly, probably about 2mm per hour. If the mine was underground or within a cave, everyone had to be out before firing began as toxic levels of CO₂, CO and SO₂ occurred and would have proved fatal to the miners. This process was known as fire-setting and weakened and loosened rocks, the introduction of gunpowder for the purpose did not occur until the 1600s. One associates miners with lamps on their hats but in some of the bigger mines the shafts were actually lit.

Tin was mined in Turkey in 2,500BC and on Mount Gabriel in County Cork during the British Bronze age about 1,500 BC. Stone hammers and antlers were used throughout the Bronze Age but were replaced later by iron chisels later which were more efficient. At Alderley Edge in Cheshire, many stone hammers have been found ranging in weight from 500g to 50kg approximately. Most are the size of half a modern day brick and were hafted on to a wooden handle with deer skin. Some larger stones were attached to ropes and swung at the rocks. Antler hammers are dense and heavy and were used like a pick and were also used to lever the samples. They were very durable and lasted for a long time. It was the characteristic scratch marks produced by their use and those of the hammers that enabled archaeologists to date the period of mining to the Bronze Age. At Alderley Edge, a group of Derbyshire cavers found a hoard of Roman coins in a mine known to have been cut in Victorian times and not associated previously with either Bronze Age or Roman excavation.

The freeze-dried body of a man was found at a mine in the Atacama Desert in northern Chile. Known as “Copper Man” his remains dated to 2,000 years ago. The mine, which contained copper chloride, is situated about 1,000 feet above the level where anything can grow, and there has been no recorded precipitation within geological records, only drying winds. All his tools including hides were found intact. The mineral atacomite comes from Tricicomata in that region of Chile.

The majority of mines of the British Isles were in S.W. Ireland, central Wales behind Aberystwyth, a few on the Isle of Man and Anglesey. Some of the Bronze Age miners did not use stone hammers, particularly in Scotland, so those mines have proved difficult to date. It has also been difficult to trace some of the Roman mines although it is known that during the hunt for copper in the Bronze Age, lead and other minerals were discarded but were later recycled by the Romans; particularly the lead. The Karst limestone of the Great Orme was rich in copper and mined during the Bronze Age and evidence of huts and round houses dating to this period have been found on the top of the Great Orme.

In the first millennium BC there was a serious increase in mechanics and science and after 500BC, there was a sudden demand for silver for coinage and by the Romans for lead.

There are no remains of smelting from the Bronze Age in Europe and this has not been explained. It is possible that they did not use a slagging technique or maybe smelted the sulphides but as the copper normally occurred as cupro-ferric sulphide, how did they remove the iron? This is a puzzle as you cannot produce iron without generating slag.

This was a very interesting lecture. The speaker obviously both knew and enjoyed his subject. The slides were good and easy to follow. There was a lot of discussion as the result of questions and it became obvious that Paul Craddock has a very broad spectrum of interests and hence could probably be invited again at a later date to enlighten us on other prehistoric or historical techniques.

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