The point of departure for the study is a single crystal of the mineral galena, from which lead and silver can be produced. The crystal was unearthed during archaeological investigations of a 12th–13th century context in Oslo, Norway. Legends and medieval manuscripts tell stories about mines and treasures close to Oslo. However, up until now there has been no confirmed evidence for the mining of rock mineral deposits in Norway before the end of the 15th century. Is it possible that people in medieval Oslo exploited local minerals and produced their own metal in the High Middle Ages? If so, how and where was this done, and what was the metal used for?
Kristoffersen uses a combination of methods from the natural sciences and traditional archaeological artefact investigations, to trace the galena crystal and medieval metal artefacts back to their geological origin. The analyses reveal that a variety of different metals and alloys were used during the Middle Ages, mainly imported from sources across the European Continent and the British Isles. More importantly, the study demonstrates that lead was extracted from galena ores in the Oslo Region, by the end of the 12th century at the latest.
In her dissertation, Kristoffersen argues that locally produced lead was linked to a small-scale craft industry and used for fishing equipment, balance weights, and a specific type of spindle whorl for spinning fibre thread. When investigated by 3D scanning, several of the spindle whorls show identical features, and they could therefore be the result of small-scale serial production. It is suggested that this local product was produced within urban households or a craft centre in the Old Town of Oslo.
The findings provide novel insights into mining and local craft traditions. The study has thus deepened our understanding of the medieval society, the utilisation of local resources, and technical advances during the Middle Ages in Norway, and Oslo in particular.
Astrid Kristine Tvedte Kristoffersen successfully defended her dissertation on 20 October 2023.
Trial lecture
Designated topic: "Metal production and consumption in Medieval Oslo within the context of contemporary European production"
Evaluation committee
- Dr. Stephen William Merkel, Vrije Universiteit Amst (first opponent)
- Dr. Irene Baug, University of Bergen (second opponent)
- Associate Professor Søren Handberg, University of Oslo (committee administrator)
Chair of the defence
- Professor Jon Vidar Sigurdsson
Supervisors
- Associate Professor Unn Pedersen, University of Oslo
- Professor Marianne Vedeler, University of Oslo
- Professor Tom Andersen, University of Oslo