Evidence for the use of bronze mining tools in the Bronze Age copper mines on the Great Orme, Llandudno Background The possible use of bronze mining tools has been widely debated since the discovery of the Bronze Age mine workings on the Great Orme in the 1980 s. Since excavation began in 1987 over 30,000 bone tools and fragments, along with 2,500 stone hammers have been unearthed, suggesting that stone and bone were the materials of choice for mining tools. Little evidence of bronze implements have been found and it has been long assumed that bronze was not used to any extent as a tool due to its value or lack of hardness. However, a review of the existing evidence in 2016 led to a reconnaissance survey and then a detailed excavation programme. This resulted in the discovery of over 1,000 fragments of bronze, mostly tiny but with some larger pieces suggesting bronze mining tools were used to a far greater extent than previously thought. Miners working on the Great Orme in 1831 found the tip of a bronze pick about 30mm long. The pick tip, currently in the British Museum is very similar to pick tips found in the Bronze Age salt mines in Hallstatt, Austria, both in appearance and metal composition. The pick tip contained approximately 85% copper and 15% tin. The higher than usual percentage of tin making the bronze hard but brittle causing the clean break seen in Figure 1. (Kerstin Kowarik, 2009) Excavations in 1988/89 by Andy Lewis unearthed several metal fragments, identified by their blue-green oxidised surfaces, from an area 20 metres below surface (Location 21) (Lewis, 1997). Analysis of the fragments confirmed these to be tin bronze (Lewis, 1997). This area was excavated in 1991 and 1992 by Geoff David, who recovered over 70 fragments of Figure 2 bronze fragments from location 21 metal (David, 1992) Figure 1 pick tip found by miners in 1831 Analysis of these fragments concluded that only 50 of them were bronze with the remaining 20 being iron. This conclusion cast doubt over the original deposition of the fragments, although the most likely cause for the iron fragments being recovered from the same context as the bronze is contamination from 18 th -19 th century mine waste. The workings at location 21, (3000 ±60 BP 1402-1055 CalBc)
have seen secondary mining activity in the roof of the passage. It is probable that overlying waste, containing iron fragments from 19 th Century activity, had been disturbed, migrating downwards into the spoil containing the bronze. A further excavation programme will be carried out in the future to test this theory. Analysis of two of the bronze fragments from location 21 by at Bradford University (Budd, 1992) suggested the fragments underwent extensive cold working and indicated a moderately high tin content. The tin content (10.7%) Recent analyses of other location 21 fragments by Williams (2018 in prep) showed variable tin levels between about 7 and 12% with the suspicion that some tin may have been lost by deep corrosion of these very small fragments. Whether a higher than average tin was added to give the picks extra hardness remains unclear. 2016 investigations Two reconnaissance trips into the mine to carry out a non-invasive search for bronze fragments lying on or close to the surface of the spoil with a small hand-held metal detector (Garrett Pro Pointer AT) were carried out in 2016 (Williams, 2016). Five randomly chosen locations were visited and seven fragments of bronze were recovered from three of the locations. Three fragments were discovered from location 21, three from a previously unexcavated area at the Figure 3, possible chisel head fragment, location 17 northwest corner of the site (location 36) with the most impressive (20mm long) from a passage between the entrance and exit of the present visitor route (location 17). The fragment from location 17 is unlike any previous fragments as it shows some of the original tools surface, possibly the splintered end of a chisel. Further studies and reconstructions of possible options are needed although it is most likely that this is a splintered fragment from the head of a chisel. From the reconnaissance trips, it seemed apparent that the presence of bronze is probably more widespread than previously thought and a more thorough search was needed. 2016 excavation programme The objective of the 2016 season was to carry out detailed excavations and analyses of mine waste from the undated but probable Bronze Age workings at Location 36, with the hope that dateable material could be recovered during the excavation. All excavated material was removed from the mine and taken to a sorting area where it was inspected at a level of detail not undertaken during previous excavations. The entrance to location 36 was uncovered in 2005 by Geoff David, however no underground excavation had been carried out. Approximately 150 metres of typically labyrinthine passages exist in this area. Most parts the tunnels have the characteristics of Bronze Age workings, however there is also evidence of reworking by miners in the 18 th -19 th centuries. Excavation work began 10 metres from the entrance where the passage was blocked to the roof with mine waste. A small side passage immediately in front of this leads into the main underground complex.
Initial excavation work suggested that the spoil was of mixed ages containing artefacts consistent with both ancient and recent mining activity, as fragments of both iron and bronze were found. Fragments of limestone showing signs of 18 th /19 th Century drill marks were also recovered from this material. In all probability, this material is the result of the re-working of a Bronze Age tunnel by miners in the 18 th - 19 th centuries. If an existing tunnel was widened the original waste and later material from drill and blast could have been removed and deposited together. A total of 686kg of spoil including several large angular rocks was removed and sorted to a point 700mm North of the initial start of the excavation, where evidence of recent mining activity was no longer being unearthed. Figure 4, excavated material transported to surface. Figure 6 mixed 19th Century/Bronze Age spoil removed Figure 5, passage filled to roof prior to excavation Beyond this point the only metal fragments recovered were bronze, fragments of drilled rock were also absent. In total 87 fragments of bronze and 6 fragments of iron were recovered from the mixed-age material.
The section was cleaned revealing a faint line on the side wall - the compacted surface of the original bronze age infill. This line can be seen just to the left of the scale in figure 6. As the section was advanced four different contexts were identified, 004-007 (figure7). The bulk of the material (004) was overlying a compacted surface suggesting the passage had been mined, partly filled and used for access, causing the compaction between the layers. Further excavation revealed little difference between the lower layers suggesting the deposition of all three (005-007) could have taken place at a similar time with simply a variation in deposited spoil. 1,027 fragments is 90.06 grams. The bulk of the material excavated (004) was far richer in bronze than the layers below although bronze was recovered from all contexts. In addition to the fragments of bronze, extensive evidence of firesetting (large amounts of charcoal and heavily reddened fragments of rock) was also discovered in 004, this was absent in the lower layers, possibly suggesting the mining of slightly softer rock where firesetting and the use of bronze wasn t necessary. After the tunnel had been mined, the miners worked their way further into the hillside where the rock became harder and the use of firesetting and bronze tools became necessary. This waste material would then have been moved out towards the entrances but deposited in the tunnel as additional entrances into the underground complex determined it was no longer needed for access. The majority of the fragments of bronze discovered are very small and were only found during post excavation processing. A few larger fragments however were recovered in-situ. Most of the fragments seem to be fractured, presumably from the head of a chisel or tip of a pick. Several of fragments show evidence of their original surface with two fragments presenting part of the shape of an original tip, although it is difficult to establish whether they are from picks or chisels. Figure 7 Contexts 004-007 The sections were advanced for a further 2.3 metres over the 2016 season, a total of 1,500kg of spoil was removed and processed, with 1,027 fragments of bronze recovered from this material, the majority being tiny. The combined weight of all An experiment of hammering the end of a bronze rod produced irregular fragments similar to those discovered (Williams pers. comm.)
Figure 8 bronze pick/chisel tip (scale-1mm squares) Figure 9 bronze pick/chisel tip (scale-1mm squares) Figure 10 typical bronze fragments (scale-1mm squares)
A system was developed for the processing of the waste material to ensure that even the smallest metal fragments could be recovered, well below the limit of handheld metal detectors. The spoil was removed from the mine to a processing area where it is initially passed through a garden sieve (5mmx10mm) to remove large fragments of rock (Figure 11) Figure 12 fine spoil removed clean granular material which was inspected in detail under the magnifier. (figure 13) Fragments of bone and stone hammers were removed and any possible bronze fragments are set aside for further inspection under a microscope with a magnification of 20X. With experience, the differences between green ore fragments and green/blue metal fragments become very distinct. Figure 11 Spoil separated after being passed through garden seive The remaining fine material was then passed through a flour sieve (1mm 2 ) to remove the fine soil (Figure 12). At this stage the remaining material was inspected with an illuminated bench magnifier with any noticeable bronze, bone or stone hammer fragments removed. Figure 13 washed material through the magnifier The material was then soaked and again passed through the 1mm 2 sieve leaving a
In addition to the fragments of bronze, several possible bronze tool marks were also discovered on the walls of the tunnel. The marks could only have been made before the now dated bronze age material was placed into the tunnel so there can be confidence that the marks were made at a similar or earlier time. The marks show signs of being made by a tool of uniform shape, most likely a bronze pick or chisel (Figures 14,15) These were very similar to The charcoal sample from 004 was identified by AOC archaeology as oak however the sample from 005 (figure 16) was used in its entirety for dating so couldn t be identified. Figure 16 charcoal fragment from 005 Figure 14 Probable bronze tool marks tool marks, previously thought to have been made by bone implements. A further study to compare various tool marks is planned A sample of charcoal from context 004 and thinner section of branch wood from 005, possibly from lighting rather than firesetting were sent to SUERC for radiocarbon dating. The resulting radiocarbon determination of 3069 ± 29 BP and 2980 ± 30 BP gives date ranges of 1414-1260 calbc (95.4% probability) and 1297-1112 calbc (94.3% probability). Random sampling From the excavations at location 36 it seems clear that bronze was being used as a mining tool to a far greater extent than previously thought. The next phase of the project is to establish if this was an isolated or widespread activity. Random sampling and processing of material from a number of locations will be undertaken during the 2017 season. One random sample - 23kg of spoil, already excavated from a tunnel 5 metres below location 17 contained 87 bronze fragments. Future work, including taking castings of tool marks and further excavation work may help us to better understand the type of tools being used. It is possible a mixture of picks and chisels were being utilised. Neil Burridge has created a replica pick (Figure 17), based on complete examples from the Hallstatt Bronze/Iron Age salt mines, including preserved handles, along with the pick tip from Great Orme, described earlier. Nick Jowett. May 2017 Figure 15 Probable bronze tool marks
References Budd, P., 1992. A metallurgical investigation of two bronze fragments from the Great Orme's Head, Llandudno: Department of Archaeological Sciences, University of Bradford. David, G., 1992. Great Orme Bronze Age Mine. Archaeology in Wales, Volume 32, p. 58. Kerstin Kowarik, A. W. R. a. H. R. A., 2009. Kingdon of Salt. First ed. Vienna: Natural History Museum. Lewis, 1997. Prehistoric Mining at the Great Orme, criteria for the identification of early mining. Bangor: University of Wales. Williams, A., 2016. Fieldwork notes, s.l.: Unpublished.