Was there mineral extraction in the Highlands in prehistoric times?

by Jonathan Wordsworth

The recent Zoom lecture by Matthew Knight on the Late Bronze Age Hoard found in a peat cutting behind Poolewe in 1877  (the talk can be viewed on the Gairloch Museum Youtube channel at Poolewe: The last Bronze Age hoard in Scotland? by Dr Matthew Knight) and the recent Feats of Clay project (http://archhighland.org.uk/feats-of-clay.asp) led by ARCH relating to a metal-working site with rare clay mould fragments found during excavations at Bellfield, North Kessock, demonstrate bronze casting was occurring in the Highlands.  Together with the Stittenham Axe Mould these are important finds for Late Bronze Age Scotland.

Stittenham Axe Mould © ARCH

But this is a speculative blog examining the possibility that there might have been copper and other ores extracted in the Highlands during the Bronze Age and is meant to stimulate research by NOSAS members on some of the ore sources.  While current research has not identified any prehistoric mining in Scotland, except possibly in South West Scotland, there is certainly nothing on the scale of the Great Orme mine in North Wales. The received wisdom is that the copper and other metals alloyed with it such as tin, zinc and to a lesser extent lead, were brought into the area as ingots from metal extracted from elsewhere in the British Isles or from further afield in continental Europe.  Recent metallurgical analyses have shown very mixed compositions for the metal tools and the recent work on the Poolewe Hoard shows at least 5 different mixes of metals to produce the surviving material (see the research results at https://www.academia.edu/44587605/Poolewe_The_last_Bronze_Age_hoard_in_Scotland).

Certainly by the end of the Bronze Age it is likely that a variety of broken or discarded objects would be thrown into the mix for melting down, making it difficult to identify the original ore source from trace element analysis.

Copper Ore in the Highlands

However research over a number of years by the British Geological Survey has mapped extensive copper ore sources in Wester Ross and some of these have even been looked at commercially (e.g. https://resources.bgs.ac.uk/meiga_reports/meiga/ae173.txt) and the ‘gossan’ at Gairloch is even used as the frontispiece for the British Geological Survey report Minerals in Britain – Copper (which can be viewed online at https://www2.bgs.ac.uk/downloads/start.cfm?id=1324)

A detailed anaysis of the copper ores in the Gairloch area was carried out in the late 1970s, though the deposits were not then deemed commercially viable.

Besshi-type copper-zinc-gold mineralisation is found in basic Lewisian rocks near Gairloch in north-west Scotland. Two laterally extensive sulphide horizons were located, one of which can be traced for over 6 km and consists mainly of iron sulphides. The other, with a length of at least 1 km, comprises a 4 m thick quartz-carbonate schist with pyrite, pyrrhotite, chalcopyrite and gold. The deposit was extensively drilled in the late 1970s. Reported grades were about 1% Cu, 0.5% Zn and 1 g/t Au which were not economic at that time. Stratabound sulphides enriched in Pb-Zn-Ba and locally copper are widespread in the Dalradian rocks of Scotland.

Commodity Profile: Copper https://core.ac.uk/download/pdf/59864.pdf.

The copper deposit and mine at Rassal (NG 8490 4328) is well known to many members of NOSAS and is protected as a scheduled monument by Historic Environment Scotland (SM5666).  The leading Welsh miner Williams who saw the deposit before 1810 (The Lead, Zinc and Copper Ores of Scotland 1921 GV WIlliams & JS Flett)  described this as the best copper ore he had ever seen.  Any surface exploitation of this ore in prehistoric times is likely to have been removed by this later but short-lived extraction of copper, though more detailed survey work might reveal some earlier evidence here.  There are a couple of roundhouses close to the mine that could potentially have been involved in processing the ore in earlier times and might repay excavation at some point in the future.

Two possible roundhouses are sited near the 18th century copper mine above at Rassal Ashwood  – see http://archaeol.wwwnlls6.a2hosted.com/wp-content/uploads/2015/07/RLUCaseStudy6_Rassal_revised_03072015.pdf

Tin

There are also significant deposits of tin occurring in the Highlands and I once tried to visit the most significant of these, an outcrop of cassiterite occurring at Carn Chuinneag (cNH 247200 884300) , with a couple of friends through a long walk in through Glen Calvie.  Unfortunately the area of tin outcrop was covered by a fresh fall of snow as we arrived towards the top of the hill. The extent of this deposit has led to it being examined for potential extraction, though again the decision was taken not to pursue commercially this further (https://resources.bgs.ac.uk/meiga_reports/meiga/ae114.txt).

Carn Chuinneag, Glen Deibidale, Ardgay, Ross and Cromarty ©NMS.

There are various youtube videos worth looking at to see how copper, tin and other metal ores were thought to be smelted (e.g. smelting copper and tin, Smelting Tin with Neil Burridge  and Prehistoric copper smelting in a pit!)

Those of you familiar with map-based data sets might wish to explore the BGS online dataset Geoindex at https://www.bgs.ac.uk/map-viewers/geoindex-onshore/ to identify areas of mineral interest in your area before venturing to look for potential mining sites. Identifying whether prehistoric mining has occurred is going to be difficult to prove, especially if the sites, as at Rassal,  have been subject to more recent mining. Pits for smelting the copper ore will be difficult to find, likely being covered by modern vegetation but grinding and hammer stones to chip out the ore may survive close by the original ore outcrop.