3.5 Metals

In Hunter, Cowie and Heald’s review of research priorities for Archaeometallurgy in Scotland (2006) they pointed out the potential for more systematic research in Scotland, particularly making the case that there has been comparative little work on metal sources, or indeed on the comprehensive examination of the wealth of artefactual evidence in museum collections. The existence of ore sources across Scotland is widely known, and there is plenty of evidence of metal working, but few have been the subject scientific excavation. It is only comparatively recently that, for example, there has been an extensive synthesis of mould and crucible fragments (Heald 2005). Likewise only a small fraction of the extensive holdings of the NMS have and been investigated analytically or technologically, with a similar situation in other major collections.

At the same time the ability of new scientific methods to obtain good precision compositional data without sampling or with micro samples has increased dramatically. While the need to ensure that any analysis is truly representational remains a key issue (ie it is not skewed by surface corrosion, inhomogeneity, applied layers etc) the feasibility of gathering large analytical data sets is now more limited by research personnel than by technique, although equipment and facilities regularly available for archaeological and historical artefact analysis remains a limiting factor.

A selection of recent work is summarised in Table 4, a list that indicates the opportunities for further work are substantial. The authors adopt and extend the recommendations of Hunter et al.:

  1. Identification and study of mines and metal sources (with a focus on proxy environmental records as a first step).
  2. Definition and interpretation of regional alloy patterns at all periods.
  3. Broad study of ironworking evidence in Scotland to produce models of its organisation, similar to the recent synthesis of non-ferrous metalworking.
  4. Metallographic study of artefacts to understand iron technology and its influences in Scotland, notably the question of any Roman influence and changes in the Early Historic/Norse period.
  5. Continuation of analytical study of precious metal artefacts from the archaeological through to historical periods to accumulate more data for investigating trade and exploitation.
  6. Technological and analytical examination of key artefacts particularly using newly available methods such as micro CT imaging.
  7. Developing links between lead ores and lead incorporated into base and precious metal alloy artefacts using lead isotopes.

Table 4: Metals: a selection of recent investigations

  Analysis Technique Publication Comment
Prehistoric gold Micro-chemical   Chapman et al 2000 Gold sources; Irish case study (Chapman et al. 2006) could be usefully applied to Scotland
Bronze Age Cu alloys Isotopic TIMS Rohl and Needham 1998  
LBA Cu alloys Chemical ? Cowie et al. 1998 Circulation zones; alloying traditions
IA/Roman iron Metallography   McDonnell 1998a, b Iron working on broch sites
Roman Cu alloys Chemical XRF Dungworth 1997 Alloying traditions
Viking and later silver Chemical XRF Kruse and Tate 1995
Eremin & Tate in Glenn,Wilthew (1995)
Silver sources and recycling zones Technology and typology
Norse Cu alloys Chemical XRF Eremin et al. 2002 Alloying traditions
Medieval and later iron and iron slag Metallography and SEM-EDAX   Photos-Jones & Atkinson 1998; Photos-Jones et al 1998 Iron technology; operation of iron bloomeries
Traditional ferrous metals Chemical and mechanical SEM-EDAX, HHXRF, mechanical stress tests Wilson (forthcoming) Conservation and maintenance of traditional ironwork (HS in partnership with Napier University)
Excavated iron   X-radiography   Excavated iron from multiple periods and sites, routinely X-rayed at NMS
Pewter Chemical XRF Wilthew et al. 1988 Survey of Scottish pewter compositions