2001 01 Centre for Archaeology Guidelines Archaeometallurgy Archaeometallurgy is the study of metalworking structures, tools, waste products and finished metal artefacts, from the Bronze Age to the recent past. It can be used to identify and interpret metal working structures in the field and, during the post-excavation phases of a project, metal working waste products, such as slags, crucibles and moulds.The technologies used in the past can be reconstructed from the information obtained. Scientific techniques are often used by archaeometallurgists, as they can provide additional information. Archaeometallurgical investigations can provide evidence for both the nature and scale of mining, smelting, refining and metalworking trades, and aid understanding of other structural and artefactual evidence.They can be crucial in understanding the economy of a site, the nature of the occupation, the technological capabilities of its occupants and their cultural affinities. In order that such evidence is used to its fullest, it is essential that Figure 1 Experimental iron working at Plas Tan y Bwlch: archaeometallurgy is considered at each stage of archaeological projects, removing an un-consolidated bloom from a furnace. and from their outset. (Photograph by David Starley) These Guidelines aim to improve the its date and the nature of the occupation. For made use of stone tools or fire to weaken the retrieval of information about all aspects of example, archaeological evidence for mining rock (Craddock 1995, 31–7) and this can be metalworking from archaeological tin will only be observed in areas where tin distinguished from later working where iron investigations. They are written mainly for ores are found, iron working evidence is tools or explosives were used. curators and contractors within archaeology unusual before the beginning of the Iron in the UK and will help them to produce Age, and precious metal working is more Little is known about how ores were project briefs, project designs, assessments likely to be concentrated at high status and/or transformed into metals in Bronze Age and reports. urban sites. Britain. Neither smelting furnaces nor slags from the smelting of copper ores have been The Guidelines are divided into a number of The following chronological summary of the recovered from Bronze Age contexts in sections. First is a summary of the sort of archaeometallurgical record for the UK England (Craddock 1990; 1994), although metallurgical finds to expect on sites of all indicates the types of evidence that are likely some slag has recently been found on the dates (p 2-4). This is followed by a section to be found. Great Orme in North Wales (Jones 1999). entitled ‘Standards and good practice for archaeometallurgy’, outlining its relationship Bronze Age In the Bronze Age copper alloy artefacts were with other aspects of archaeological projects Copper alloy and gold artefacts of this period produced by casting and smithing. Clay (p 4). Then come the fully illustrated show that these metals were worked. Some mould or crucible fragments have been found sections describing archaeometallurgical evidence exists for copper mining, while on many Bronze Age occupation sites and a processes and finds: for iron (p 9), copper other evidence demonstrates working, mostly few have produced large quantities of these and its alloys (p 15), lead (p 18), silver and casting, of copper alloys. There is almost no objects, for example Dainton, Devon gold (p 19), tin (p20) and zinc (p 21). A direct evidence for how other metals used (Needham 1980), Jarlshof, Shetland shorter section on non-metallurgical high during the Bronze Age were obtained. It is (Hamilton 1956) and Springfield Lyons, temperature processes illustrates finds that generally accepted that the tin ores in south- Essex (Buckley and Hedges 1987). However are often confused with metalworking debris west England were exploited from the Bronze finds of this type are rare in Early Bronze (p 21). A glossary of common metallurgical Age onwards but there is little direct evidence Age contexts. terms is provided (p 23). Finally come for this (Penhallurick 1997). sections introducing some of the scientific Some evidence for iron working has been techniques commonly used in Evidence for mining can only be expected in found in contexts that are culturally assigned archaeometallurgy (p 23) and a list of regions where ores are found. In England, to the Late Bronze Age. specialists who may be able to advise on copper ores are known in Cornwall, Devon, archaeometallurgical aspects of Shropshire, Staffordshire, Cheshire, North Iron Age archaeological projects (p 26). Yorkshire and Cumbria, and other sources Iron Age settlement sites generally provide are known in mid and north Wales more evidence for metalworking, and for a What to expect (Timberlake 1991). Old workings and wider range of metals, than Bronze Age sites. hammer stones (Pickin 1990) have been It is useful to know what sort of discovered during more recent mining and Iron ores, unlike copper ores, are found in archaeometallurgical evidence to expect from similar evidence has been recovered during many areas and iron mining and smelting a particular site. This depends on a number archaeological excavation of Bronze Age could be carried out on a small scale almost of factors, such as the location of the site, mining sites (Lewis 1990). Early working anywhere in Britain. No Iron Age iron mines 2 Archeo guidelines v10 hi res 28/6/02 11:45 am Page 3 are known, but bog ores and other surface of metalworking. These gradually developed structures and occupation layers have been outcrops were probably exploited. Only a few to incorporate some ‘Roman’ techniques. preserved, for example at Caerleon sites have so far yielded furnaces and large (Zienkiewicz 1993). Where workshop remains quantities of iron smelting slag, for example Roman are well preserved there is often evidence for Brooklands, Surrey (Hanworth and Tomlin A great variety of evidence for Roman a range of both ferrous and non-ferrous 1977), Welham Bridge,Yorkshire (Halkon and metalworking has been found throughout metalworking. Millett 1999) and Bryn y Castell and Britain. Any substantial excavation of a Crawcwellt, Gywnedd (Crew 1986; 1998). Roman period site is likely to recover The best known evidence for Roman lead some evidence. production consists of large inscribed lead Evidence for iron smithing is much more ingots, but some large litharge cakes, widespread, as at Dragonby, Lincolnshire Roman sites with large numbers of furnaces showing that silver was extracted from lead, (May 1996) and Scalloway, Shetland and huge quantities of iron smelting slag have have also been found in the Mendips and (Sharples 1999). Iron smithing can also be been discovered in the Weald of Kent and Welsh borders, for example at Pentrehyling indicated by cut fragments of iron stock and Sussex, for example at Bardown and Beauport (Bayley and Eckstein 1998). Small litharge hoards of blacksmiths’ tools – for example at Park (Cleere 1974). Other major iron smelting cakes, produced during the extraction of silver Waltham Abbey, Essex (Manning 1991) – centres existed in the Forest of Dean, from debased alloys, are also often found on while the microstructure of finished objects Northamptonshire and Lincolnshire but iron urban sites. provides information about the smiths’ smelting evidence has also recently been found techniques (Salter and Ehrenreich 1984). in other areas, such as at the Blackdown Hills, The only evidence for tin mining in the Important information on the use and trade Devon (Griffith and Weddell 1996), and can Roman period is the occasional inscribed of different types of iron stock can be be found almost anywhere. Iron smithing slags ingot. The casting of pewter is fairly well obtained from currency bars, for example the are routinely discovered on almost all Roman known from stone moulds that have been hoard found at Danebury, Hampshire sites, and occasionally blacksmiths’ workshops recovered from both urban and rural sites (Cunliffe 1984), and from more rare smithed are found, for example at Ashton, Northants (eg Blagg and Read 1977). blooms and billets. (Hadman and Upex 1975). Roman-period gold mining is known Most English Iron Age settlement sites have A number of large, circular, stamped copper from Dolaucothi, Dyfed (Burnham 1997). yielded some clay mould or crucible ingots have been found, particularly in Wales Parting vessels, for separating silver from fragments for casting copper alloys but a few (Kelly 1976), although no evidence of copper gold, have been found on a few urban sites sites, including Gussage All Saints, Dorset mines, furnaces or slag involved in their (Bayley 1991a). (Wainwright 1979) and Grimsby, production has yet been discovered. Lincolnshire (Foster 1995), have produced Specialised crucibles for brass production have Early medieval large assemblages. Coin manufacture can be been identified on a few urban sites (Bayley Both urban and rural settlements produce a demonstrated at a number of oppidum sites, 1984). Clay moulds and crucible fragments great variety of evidence for the working of such as Verulamium (St Albans), are relatively common finds on many Roman many different metals. The finds are not all the Hertfordshire (Frere 1983), and there was sites and occasionally the evidence is same in the different cultural areas of the possible silver production at Hengistbury particularly abundant, for example at British Isles (Bayley 1992c). Head, Dorset (Northover 1987). Castleford (Bayley and Budd 1998). Stone and metal moulds are also known, but are far A variety of iron smelting technologies, which Those parts of Britain that were not within less common. A number of workshops have produced distinctive types of slag, were in use. the Roman Empire kept Iron Age traditions been discovered in which a variety of Large slag blocks have been found at a number of sites, including Mucking, Essex and Aylesham, Norfolk (Tylecote 1986, fig 81), while at Ramsbury, Wiltshire (Haslam 1980) both non-tapping and tapping furnaces were found.