Smelting of Sulfide Ore During the Bronze Age in the Eastern Alpine Region
A mining, archaeological and experimental approach
The mining district of the Mitterberg area played an integral role as a supplier of copper ore during the Bronze Age in the eastern Alpine Region as well as farther abroad. Research in the area, which spans more than 150 years, has provided a wealth of information not only of the underground traces of prehistoric mining, but also of the above ground ore extraction, beneficiation and smelting sites which are scattered throughout the mountain landscape. In spite of the long research tradition, comprehensive knowledge of the mining economy of the Mitterberg area as a whole is still lacking.
Based on a multi-disciplinary networking of researchers, a FWF-funded special research program HiMAT (The History of Mining Activities in the Tyrol and Adjacent Areas – Impact on Environment and Human Socieites), was formed in 2006 in order to investigate the supra-regional ore production landscapes that developed in Tyrol and adjacent regions. As part of this larger project, the Mitterberg area is being reevaluated using an array of modern systematic surveys and excavations, with the goal of evaluating the environmental, temporal, logistic and technological basis of the local economy. In addition to targeted excavation of both above and below ground features, broader surveys including geophysical prospection and sediments core profiles will bring new information about the age, size, volume, chemical and botanical composition of the ore extraction, beneficiation and smelting sites as well as their location within the local environment.
The objective of the present dissertation is to combine the results of past and current research into a holistic synthesis of the economical factors that distinguish Bronze Age smelting sites in the eastern alpine region. The first stage of research aims to collect information from the literature and field research about copper ore smelting sites in the eastern alpine area, using the finds from the Mitterberg region as a case study. The sites will be examined in relation to their surrounding environment, including their proximity to the exploited ore body, accessibility to water and fuel, as well as their relationship to known contemporary settlements and trade routes. The physical remains of the smelting process, i.e. ore roasting beds, furnaces, tuyères, ore fragments, slag, etc. will also be critically reviewed to determine if the technology is as homogeneous throughout the alpine region as traditionally believed, and if not then to define regional and/or temporal differences within the smelting operation.
With the incorporation of the results from the above mentioned research project, detailed information of several smelting sites within a mining district are being collected using a combination of field and geomagnetic surveys, coring and spot sampling. Field surveys give information about the sites’ location and proximity to local resources. Geomagnetic survey of the sites has proven to be very effective in ascertaining the extent of the smelting site, even where only few physical remains are visible on the surface, as well as the probable location of the pyrotechnical installations (ore roasting beds and furnaces). Systematic coring supplies information about the composition of the anomalies seen in the geomagnetic survey, and the thickness of the cultural deposits. Spot sampling of the sites brings additional information about the composition and volume of the slag heaps as well as mineralogical, typological, and chemical composition of the slag, which can give evidence of the furnace charge, specific thermal conditions within the furnace and possibly interrelationships between the smelting sites and specific ore occurrences. The chronology of individual smelting sites will also be discussed, through the use of C-14 dating, in order to clarify the transformation of the mining district through time.
The second step deals with the reconstruction of the smelting procedure. In light of the archaeological evidence and ethnographic examples, previous theoretical and practical reconstructions of the alpine smelting process will be critically reviewed, their feasibility deliberated, their advantages and disadvantages carefully deconstructed. An in-field reconstruction of a Bronze Age alpine smelting furnace is also planned in which specific criteria which have not been preserved in the archaeological record can be tested – i.e. placement of the tuyères and number of bellows used, the existence (or absence) of a front wall, reconstruction of the furnace height, composition of furnace charge and length of the smelt, etc. The experimental smelting products will then be compared with archaeological remains, their similarities and differences discussed. The ore:metal:slag ratios of the experimental smelts will also be used as a guideline for the theoretical calculation of the production volume of the archaeological smelting sites.
Through the use of past and modern archaeological research, ethnographic examples and experimental archaeology, it is hoped that better understanding of the Bronze Age smelting process will be achieved, as well as a holistic view of the economical factors that played a role in Bronze Age copper production in the eastern Alpine Region.
Dr. des. Peter Thomas
Studien zu den bronzezeitlichen Bergbauhölzern im Mitterberger Gebiet
Deutsches Bergbau-Museum Bochum