Iron Pieces from The Copper Wreck : An archaeometallurgical analysis of iron bars, billets and osmund iron found in Gdansk, Poland

Abstract: The topic of osmund iron is of great interest in both historical and metallurgical perspective. Between the 14th and the 17th century osmund iron was exported extensively from Sweden but it has been difficult to characterize and confirm what exactly osmund iron is. Further research should be conducted to improve the understanding of this kind of iron.   This work is primarily focused on medieval osmund iron. It is trying to determine what can be stated about their production methods and how to identify osmund pieces. A literature review was performed, to present an overview of iron production methods in medieval Europe. A metallurgical analysis was conducted on a number of osmund samples from the polish shipwreck ‘Miedsiowiec’, W5., together with samples from bar irons and iron billets from the same ship. Analysis was performed using LOM and SEM with EDS, analysing the crystallographic structure of the samples, and performing slag analysis using EDS to establish statistical trends. One of the aims was to evaluate a previously suggested hypothesis, namely that osmunds were shipped to Danzig from Stockholm, and then refined into iron bars and billets.  The studied iron bars and billets were purely ferritic with some slag inclusions. By looking at the shape of the slag inclusions, it can be stated that the bars and billets were forged differently from the osmund pieces. The osmunds were found to be made by indirect reduction as seen by the prevalence of cementite. It could not be confirmed if the bars and billets were forged by osmunds.  The osmunds showed different trace element compositions, than the iron bars and billets. The microstructure of all the osmunds varies greatly, which was to be expected. The osmunds had a higher carbon content and fewer slag inclusions. The hypothesis that osmunds were refined into iron bars and billets is not supported by the findings of this study.