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Comet Lode - Copa Hill

 

An ancient scree-filled opencast working some 50 m long and of unknown depth (but >15 m) excavated at the top of the Comet Lode. The mineral veins here carry galena (lead sulphide) and chalcopyrite (copper iron sulphide) within an iron carbonate and quartz gangue.

The presence of “ancient workings” and stone mining hammers at this location was first recorded in 1813, and in 1937 Oliver Davies re-examined this old site for the evidence of early mining on behalf of the British Association for the Advancement of Science. He concluded that the mine was Roman or “old Celtic” in origin.

 

Mining on Copa Hill circa. 2000 BC Brenda Craddock

 

 

The first modern excavations at this site were undertaken by Simon Timberlake in 1986. A 12 m section was cut through the Central Tip exposing stone tools and buried charcoal layers from which three Bronze Age radiocarbon dates were obtained (Timberlake & Switsur, 1988)

 

The Early Mines Research Group carried out excavations within the opencast between 1989 and 1999, uncovering a landscape of rock-cut benches and pillars, a mine gallery with the marks of stone tool use in its roof, emptied vein fissures as well as an entrance or drainage cutting to the workings which lay buried beneath many metres of weathered scree, peat and silt, plus slumped-in and backfilled mine waste.

 

Marks of stone tool use on roof of mine gallery.

 

 

The gradual infill of this mine had been taking place since well before its abandonment in about 1600 BC, after most of the copper mineral had already been removed.

 

 

The mine seems to have been suffering severe problems of flooding from at least 1850 BC, some 200 years after its discovery at the beginning of the Early Bronze Age

 

Excavations have uncovered a unique series of hollowed-out wooden logs of alder and oak which were used as drainage launders (gutters) to tap the water issuing from springs within the rock walls of the working, and then to guide this out of the mine.

 

One  5 metre section of 4000 year-old launder was found still in situ. within the entrance cutting, preserved here due to the waterlogged conditions and the high level of metal it contained.

 

 

Other organic artefacts such as red deer antler picks and hammers, fire-sticks, hazel withy handles for the hammer stones, rope, basketry fragments etc. were also preserved.

 

 

red deer antler picks and hammers

 

 

hazel withy handles for the hammer stones

 

 

The miners had used simple stone cobble tools which they had brought with them from the coast together with cut oak stemples for climbing down into the veins and oak brushwood for fire-setting, a technique to soften and break-up the hard quartz-rich rock.

 

 

In some places the lead ore had also been removed, but most of this was discarded alongside the veins or in the waste heaps, either as lumps or else as crushed-up material.

 

 

Some of the galena may have been intentionally extracted as lead ore is easy to smelt and work, even though there seems to have been little use made of it during the Early Bronze Age in Britain.

 

This together with and the clear evidence for the extraction and fine crushing of the rather more difficult to smelt chalcopyrite, plus the lack of any evidence at all for further processing, smelting or habitation evidence, remains one of the many mysteries which surrounds this site (Timberlake 2003).

 

 

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Some 4-5 metres of this infill was sectioned; with radiocarbon dates and environmental evidence revealing an abandonment history, spanning some 3500 years.

 

It seems possible that the crushed copper-bearing vein material may have been washed and just the oxidised (green) copper minerals extracted from it, this then would have been removed for smelting away from the mine.

The wooden log launders may also have been used for washing and separating the lead from the copper, and the sulphide from the carbonate fraction of mineral.

A possible reconstruction of this process is shown below.

Withy rope or tie