REGIONAL VARIATIONS IN BLOOMERY SMELTING SLAG OF THE IRON AGE AND ROMANO‐BRITISH PERIODS*

This study highlights regional variation in the composition of iron‐smelting slag produced in England prior to the medieval period and attempts to link slag composition to the type of ore smelted. For many sites, the slag compositions were consistent with the use of limonite ore, but there is evidence that siderite ore was smelted at sites in Sussex in the late Iron Age/Romano‐British periods. A compositional comparison of smelting slags and slag inclusions in Iron Age currency bars, using data from Hedges and Salter (1979 ), illustrates the potential of smelting slag compositional data in provenance studies of early iron objects.     

Prehistoric iron production technologies in the Upper Thai-Malay Peninsula: metallography and slag inclusion analyses of iron artefacts from Khao Sam Kaeo and Phu Khao Thong

This article presents a preliminary attempt to characterise Upper Thai-Malay Peninsula prehistoric iron technologies based on assemblages from two recently excavated coastal sites: Khao Sam Kaeo and Phu Khao Thong. These are the earliest known sites involved in the early trans-Asian exchange that connected the eastern Indian Ocean to the South China Sea from the mid-first millennium bc. It is from this period that iron assemblages start appearing at both continental and insular Southeast Asian sites. Three models have been offered confronting an indigenous vs. Chinese or South Asian impetus for the introduction of iron metallurgy in Southeast Asia. These models are discussed in the light of the metallographic and compositional analyses of iron and slag assemblages from these two sites using optical microscopy, scanning electron microscopy with energy dispersive spectrometry, energy dispersive X-ray fluorescence and slag inclusion analysis techniques, together with other production materials from these and other contemporaneous Southeast Asian sites.     

Saami Circular Sacrificial Sites in Northern Coastal Sweden

Abstract

Saami circular sacrificial sites have been known for many years in northern Norway and northern interior Sweden. Oral or written sources regarding their origins are nevertheless lacking outside reindeer-herding areas. These circular features have now been documented in Swedish Bothnian coastal environments together with site complexes at elevations, suggesting that they were used during the Iron Age, medieval and historic periods. It is argued that these coastal features, stone circles or ring-shaped enclosures, are Saami sacrificial sites of the same character as documented in North Norway and in the mountains and the forest lands of northern Sweden.     

Mineralogical And Chemical Investigations Of Bloomery Slags From Prehistoric (8th Century Bc To 4th Century Ad) Iron Production Sites In Upper And Lower Lusatia,Germany

More than 400 fayalitic bloomery slags from prehistoric iron production sites in Upper and Lower Lusatia, eastern Germany, as well as bog iron ore samples and intermediary samples of the smelting process, were analysed by chemical and mineralogical techniques. While the precursor bog iron ores exploited in the two regions under investigation were very similar in composition, consisting of low‐manganese/low‐barium as well as high‐manganese/high‐barium types of ore, pronounced differences in slag composition were detected. Slags from 17 investigated sites in Upper Lusatia showed average P₂O₅ contents between 1 and 3 mass%, whereas slags from 15 investigated sites in Lower Lusatia were generally much richer in phosphorus, reaching values as high as 7 mass% P₂O₅. Since a reasonable correlation exists between calcium and phosphorus contents in the slags of the latter sites, it is conjectured that deliberate addition of CaO to the ore/charcoal charge of the bloomery furnace may have taken place in order to fix the phosphorus in the slags effectively. In many samples, this conjecture is being supported by the detection of a slag mineral Ca–Fe phosphate Ca_9?xFe_1+x(PO₄)₇ that presumably crystallized from a residual phosphorus‐rich melt and shows a cotectic relationship to both Ca‐rich fayalite and wustite, as well as to members of the solid solution series magnetite–hercynite.     

METALLOGRAPHIC STUDY OF IRON ARTEFACTS FROM THE EASTERN TRANSVAAL,SOUTH AFRICA

The microstructures of two adzes, two hoes and a spear point from Iron Age settlement sites in the Kruger National Park have been examined. Electron microprobe analyses of the slag inclusions were also made. Some of the objects are made of high carbon steel while others have a highly variable carbon content. All appear to have been forged at relatively low temperature and then annealed at a low temperature near 700°C. None have been hardened by quenching and tempering. Some of the objects contain only traces of included slag while others have large slag inclusions. The slag compositions are quite different from those of medieval bloomery slags and are representative of African iron smelting practice in their high content of CaO, K₂ O and Na₂O. On the basis of the titanium content of the included slag, two of the objects are identified as made of the ore from Rooiwater and one from Phalaborwa ore.     

Farm mounds of the harstad area

The farm mounds of coastal North Norway are settlement accumulations produced by long period settlement on the same location. The majority seems to have come during medieval and later periods, but there are a few of early iron age origin.

There has been no total excavation of a farm mound, only minor trenches. This paper summarizes the efforts done on exploring the context and characteristics of farm mounds, based on surveys in one central part of North Norway, the Harstad area.

Questions like economical reconstruction and causes of accumulation are discussed.     

Iron production in scandinavian archaeology

Several sites of the historic and prehistoric periods exist at the vicarage of Borg on Vestvåg?y, North Norway. The settlement site Borg I, which is at present being investigated within the framework of a Scandinavian research project, is believed to be a Late Iron Age chieftain's residence.     

Pastoralist iron production on the Laikipia Plateau, Kenya: wider implications for archaeometallurgical studies

Recent research conducted on the Laikipia Plateau in Kenya highlighted several shortfalls in the existing models for understanding and interpreting past iron production technologies. The research was undertaken in order to assess variability in past pastoralist iron production techniques – the first such archaeometallurgical exploration in the region. In all, seven furnaces and one iron production refuse area were excavated across two discrete sites separated by only 3 km: Mili Sita and Cattle Dip, both dating to the second half of the second millennium AD. The recovered archaeometallurgical materials – slag, furnace wall, and tuyères – were analysed using a combination of optical microscopy, SEM-EDS and ED-XRF.The results revealed that the technologies in question were complex and sophisticated, and their reconstruction and interpretation required some special considerations. The exploitation of titania-rich black sand was observed to bear a major influence on the resulting slag compositions at both sites, and use of these specific materials resulted in consistently efficient smelting episodes, demonstrating the technical competence and skill of the past smelters. However, although the slag compositions and microstructures of all the samples were markedly similar between the two sites, striking stylistic variation was apparent in the furnace design. This raised questions not only about the organisation and identity of the smelters who were working in this area at this time, but also of the reliability of assuming that similar slag compositions – peculiar as these might be – reflect similar technological (or sociotechnical) systems (cf. Pfaffenberger, 1992). A further problem encountered was that the consequently ulvite-rich slag was comprised of five, not three, major constituents – titania and lime in addition to iron oxide, alumina and silica. This meant that the operating parameters of these smelting episodes could not be easily interpreted using the usual models, which tend to be based around the assumption of fayalitic slag.As such, this paper will discuss to what extent consistency in technological style, in a broad, sociocultural sense, can be inferred through slag analysis, as well as the need for the formulation of wider reaching models that encompass the full scope of technical variation in iron production.     

Mesolithic in South‐Eastern Norway

This article discusses the reliability of shore‐line displacement curves based on pollen analysis in the Oslo Fjord area. The conclusion is that only small parts of the curves ‐ in the late Atlantic period ‐ are fairly reliable for the purpose of dating Mesolithic coastal sites.

Twelve Mesolithic settlement sites from Østfold, south‐eastern Norway are classified morphologically. The author suggests a chronological lineal model with four succeeding phases: 1. The Fosna culture, 2. Late Boreal/early Atlantic group, 3. The N?stvet culture, 4. Late flint‐point using group. A connection between the Fosna culture and early Maglemose culture is claimed.

A study of the ecological adaptation in the four phases is based on topographical conditions, on the distribution and situation of settlement sites, and on animal bones from three Mesolithic sites in south‐eastern Norway. Hypotheses on seasonal migrations are suggested.     

Iron and bronze production in Iron Age IIA Philistia: new evidence from Tell es-Safi/Gath, Israel

A metallurgically-oriented excavation in Area A at Tell es-Safi/Gath yielded evidence for iron and bronze production dating to the early Iron Age IIA. Two pit-like features, which differed considerably from one another in colour, texture and content, were excavated. Evidence shows that each feature represents a different in situ activity related to iron production, inferred by the presence of hammerscales, slag prills and slag. An upturned crucible was found on top of one of the features. Analysis of the crucible slag showed that it was used for bronze metallurgy. Tuyères, both round and square in cross-section, were found in and around the two features. The presence of the two industries together presents a unique opportunity to explore the relationship between copper and iron working. This is especially important against the background of the scarcity of evidence for iron production in the Levant during the early phases of the Iron Age.     

Variability in single smelting episodes – a pilot study using iron slag from Uganda

Most archaeometallurgical studies of iron smelting are based on the analyses of slag fragments randomly selected from slag deposits, and assume that these samples are representative of the typical smelting conditions of the given context. However, little archaeometallurgical research has been published to explore the variability in slag composition within a single smelt, or between individual smelts at the same production site. The material used in this pilot study originates from two iron smelting sites identified in the Buganda Kingdom, Uganda, dated to the 18th and 19th centuries AD. The remains represent evidence of the industrial scale iron production that supported the growth and power of the kingdom. The slag survives in large clusters of complete blocks, in some cases weighing over 100 kg, each resulting from a single smelting episode in a pit furnace. A multi-sample analytical approach has allowed an insight into the compositional diversity within the slag from single smelting events, reflecting changing parameters in the smelting systems. The internal variation of the slag blocks is subsequently compared within and between sites, to address issues of standardisation and to differentiate two technological traditions that would appear very similar at the macroscopic level. On this basis, some sampling recommendations are made for future slag block studies.     

THE TUNGSTEN AND TIN SIGNATURE OF IRON ORES FROM ELBA ISLAND (ITALY): A TOOL FOR PROVENANCE STUDIES OF IRON PRODUCTION IN THE MEDITERRANEAN REGION

The mineralogy, petrography and major‐ and trace‐element composition of iron ores from Elba Island (Tuscany, Italy), one of the most important iron sources in the Mediterranean area since the first millennium bc , revealed that hematite‐rich ores display prominent enrichments in W and Sn (up to 4950 μg g^?1 and 8400 μg g^?1, respectively). These two elements are hosted by tiny grains of W–Sn mineral phases (ferberite, scheelite and cassiterite) that are disseminated throughout the hematite matrix. A comparison with iron ores from many Italian and European localities (most of which were exploited in ancient times) suggests the uniqueness of the geochemical pattern of Elba Island hematite‐rich ores (i.e., high W and Sn, low Mo and low Cu, Pb and Zn). We suggest that this geochemical signature may represent a new provenance marker not only for discarded ore at smelting/smithing sites, but, possibly, also for metallurgical slag and smelted metal produced in the chaîne opératoire of the iron process.     

Identifying stone tools used in mining,smelting, and casting in Middle Bronze Age Cyprus

Abstract

Metallurgical production sites are often difficult to identify in the archaeological record because ore beneficiation and slag processing in the past involved the use of ground stone tools that were similar to those used in other contexts to prepare cereals and foods. Analysis of the ground stone assemblage from a Middle Bronze Age copper mining and production site at Ambelikou Aletri in Cyprus provided an opportunity to distinguish industrial and domestic ground stone tools and to identify the types of tools used in different stages of metal production. A comparison of tool morphologies, raw materials, and wear and breakage patterns from Ambelikou Aletri with those from contemporary domestic contexts, suggests that distinctions in the nature and structure of industrial and domestic tool kits do exist and those distinctions have an important role to play in identifying mining, smelting, and casting sites in the future.     

Iron Working in the Vicinity of Weybridge,Surrey

Abstract

The presence of eighteenth-century iron working mills and the coincidental local, but limited, source of iron in the Weybridge area of Surrey, has led a number of authors to suggest that these mills smelted locally extracted iron ore. The present author has described elsewhere the occurrence of the ore and indicated that extraction was in pre-mediaeval times, probably during the Iron Age. In further support of this theory, the original records of Iron Age archaeological sites in the area are shown to reveal positive evidence of iron working. The history of the iron mills throughout their restricted period of iron working is also described, and at each site a close association between the fabrication of iron, and brass and copper products, where the metal is of undoubted extraneous origin, is evident.     

WROUGHT IRON FROM THE USS MONITOR: MINERALOGY,PETROLOGY AND METALLOGRAPHY*

The metal and its slag inclusions from the USS Monitor are mineralogical and geological artefacts of a vessel that has catalysed and documented the technology of maritime construction and warfare since 1862. Petrological study of a wrought iron disc from the hull of the Monitor reveals low‐carbon, high‐phosphorus ferrite with 4.8 vol% silicate slag, which includes phosphoran olivine, glass, wüstite and a silica polymorph. The sample, although made at the height of wrought iron manufacture, is of only mediocre quality and has a mineralogy, petrology and metallography that reflect the latter stages of puddling, rolling, annealing and 140 years of corrosion.     

Monitoring Cultural Heritage in a Long-Term Project: The Norwegian Sequential Monitoring Programme

Abstract

A sequential monitoring programme for archaeological sites and monuments was started in Norway in 1997. The purpose of this ongoing monitoring was to produce more accurate figures for loss and damage and to detect long-term trends in loss/damage patterns. In this article we present the method used to document the sequential monitoring, the extent of and the most important causes of loss and damage to archaeological heritage, and we discuss both the strengths and weaknesses of the method used in this monitoring programme. The results so far point to agriculture as the single most important cause of loss, and together with housing and leisure it is also the most important cause of damage. In the large parts of Norway where agriculture is marginal and has been characterized by small farms and grass based livestock production, regrowth of fallow fields leads to cultural landscape change and the loss of archaeological sites.     

Hesitant hunters: a review of the introduction of agriculture in western Norway

Abstract

Evidence for the introduction of agriculture in western Norway is presented, using three categories of data: (1) palaeobotanical data, including pollen diagrams from lakes, bogs and archaeological sites, focusing on the presence of cereals, Plantago lanceolata L. and anthropogenic pollen indicators, and charred macro remains of cereals from archaeological sites; (2) osteological data, focusing on the occurrences of bones of cattle, sheep and goats in three rock-shelters, and the bone material from one open-air Neolithic site; (3) archaeological data, including artefacts indicating agricultural practices, distribution of residential settlement sites, and stray finds. The evidence for agricultural activity at the beginning of the fourth millennium BC (Early Neolithic, EN) is low, whereas the presence of both cereals and animal husbandry is indicated in the palaeobotanical material from the Middle Neolithic A (MNA, 3400–2600 cal. BC). The earliest record of domesticated animal bones is dated to the Middle Neolithic B (MNB, 2600–2200 cal. BC), while palynological and archaeological data also indicate an expansion in the area cultivated by early farmers. All data confirm the establishment of an agrarian society and animal husbandry in the Late Neolithic (LN, 2200–1700 cal. BC). It is concluded that agriculture was introduced into western Norway by the indigenous hunter-fisher populations. During this process, social and ideological factors played principal roles.     

Slag inclusions in iron objects and the quest for provenance: an experiment and a case study

Slag inclusions are found within most archaeological bloomery iron artefacts and are remainders of slag created during the smelting and smithing processes. Although they are widely believed to provide data with the potential for provenancing iron artefacts, previous slag inclusion studies have mostly proven inconclusive. The main aim of the work reported here is to analyse experimental smelting and smithing assemblages (including ore, furnace lining, fuel and slag), to compare these to slag inclusions in the resulting bloom and worked objects, and then explore the relationships between ore, slag and slag inclusions. This study has revealed that the composition of slag inclusions most closely relates to the smelting slag produced, whereas provenance to a specific ore would be difficult due to the chemical variability derived from furnace lining, fuel and any fluxes used. Some compounds in the slag inclusions are particularly affected during smithing of the artefact, i.e. those present in the sand flux and fuel used. However, trends are observed in the K₂O/MgO, MnO/SiO₂, Al₂O₃/SiO₂, Al₂O₃/MgO, Al₂O₃/K₂O and Al₂O₃/CaO ratios that allow comparison between slag inclusions and smelting slag in these experiments, and may therefore be used during other provenancing attempts. The knowledge gained from the experimental assemblages was subsequently applied to an archaeological case study, examining objects from the 900 Cal BC smithing site of Tel Beth-Shemesh, Israel and the 930 Cal BC smelting site of Tell Hammeh, Jordan. The analyses suggest that none of the artefacts examined derived from the Hammeh smelting system.     

Charcoal analysis of industrial fuelwood from medieval and early modern iron-working sites in Bilsdale and Rievaulx,North Yorkshire,UK: evidence for species selection and woodland management

Abstract

This paper presents the results of species diversity and dendrological analyses of archaeological charcoal excavated from medieval and early modern iron production sites in Bilsdale, and at Rievaulx in the neighbouring valley of Ryedale, North Yorkshire, UK. Standard methods of quantification are used to assess species diversity, sampling sufficiency and taxa presence. The assessment of dendrological features provides additional evidence for growth trends and cutting cycles analogous with cyclical woodland management, as well as environmental and growing conditions. Analysis of archaeological charcoal from four medieval bloomery furnace sites in Bilsdale, and from the site of the hammersmithy and blast furnace at the early modern iron works at Rievaulx, provide comparable data-sets which indicate a change in cutting practise and dominant species selection for industrial fuelwood occurred between the 12th- and mid-16th centuries AD. Results show that dominant species presence changed from an admixture of predominantly birch (Betula sp.) and hazel (Corylus avellana) sourced from small calibre branchwood and stemwood used in the medieval bloomery furnaces, to a dominant oak (Quercus sp.) presence from standard sources used at the Rievaulx iron works by the mid-16th century. Whilst it is uncertain whether this change in dominant species composition and the source of industrial fuelwood is related to changes in local availability, or the result of the technological transition to blast furnace processing which occurred at this time, estate records reveal a woodland management campaign was instigated to supply and maintain fuelwood supplies to the iron works at Rievaulx which coincides with the introduction of Tudor arboricultural legislation in the 1540s.     

THE PROVENANCE OF IRON ARTEFACTS FROM MANCHING: A MULTI‐TECHNIQUE APPROACH*

Iron finds from the Celtic oppidum of Manching in southern Bavaria (Germany) are analysed in view of their possible provenance. The exceptional size and the location of Manching are usually attributed to the presence of abundant iron ores in its vicinity. After a review of previous approaches for source determination of iron artefacts, we introduce lead isotope analysis as a new approach. However, only by combining the trace element patterns of slag inclusions and iron metal with lead isotope ratios in the metal is it possible to distinguish various iron ore formations near Manching. As a result, it turns out that, indeed, the most obvious ones—namely, bog ores near the Danube—constituted the main resources for iron production at Manching. It was even possible to select one occurrence as the most likely ore source.