Viking Age Steatite in Sweden: Accessory Mineral Provenancing and the Biographical Approach

Abstract

Part 1 of this thesis discusses the Swedish steatite artefact assemblage from a biographical approach; its formation, quarrying, and transformation to household objects, its interactions with people during the journey, and the distribution patterns of the assemblage. This sets the stage for Part 2, which presents a new, interdisciplinary approach for steatite provenancing: LA-ICP-MS trace element composition maps of accessory minerals in steatite. The specific accessory minerals that grow in steatite as it forms, and which trace elements get locked into their crystal structure, is a function of the temperature and pressure under which it formed, and how/if those conditions changed during the formation process. Therefore, while a single steatite quarry displays differences in the proportions of the major minerals present, which can translate to large changes in whole-rock compositions across the quarry, its accessory mineral “fingerprint” is more consistent.

These trace element maps reveal the “fingerprints” for steatite accessory minerals from quarries across Sweden and Norway which confirm the hypothesis that the patterns of trace element distribution within a given accessory mineral matches those in other samples from the same quarry (same pressure-temperature history), has both features similar to and different from those of samples from the same tectonic rock unit (partially overlapping pressure-temperature history), and is quite different from those from different tectonic rock units (different pressure-temperature history). These “fingerprints” can be used to confirm that a steatite artefact could have come from a specific quarry, as with the Medieval Trondheimskleber building stone from Nidaros Cathedral, or to demonstrate that a steatite artefact did not come from any of the analysed quarries, as with the two Hedeby artefacts analysed (Chapter 8).

As more steatite quarries and artefacts are analysed to produce such trace element composition maps, the precision of the provenancing will continue to be refined.

Supplementary files associated with the thesis can be accessed at: https://zenodo.org/communities/la-icp-msmaps/