From erratic boulders to sacramental emblems - the geocultural significance of millstones embedded in the walls of Gothic churches in the Southern Baltic Lowlands

Northern Poland and North-Eastern Germany are unique in the World regions with such a large number of Gothic churches, in which walls old querns and millstones were embedded and exposed. Already the very idea of sacralising such stones, which were commonly used in hand mills, water mills and wind mills, is fascinating. There are several concepts as to why they were inserted into the walls of churches. One of them refers to the idea of the so-called Eucharistic Mill, popular in German-speaking area during the Middle Ages. An object used to make bread could not simply be thrown away after being used up.  Thanks to the fact that these stones were set into the walls of churches as early as the Middle Ages, we have an exceptional opportunity to learn about the degree of advancement in the technique of their production, use and conservation in the 13th to 15th centuries. At the same time, we were able to identify several examples of erratic boulders (in situ) with traces of production for millstones.

We identified more than 70 querns and millstones. Almost all of the examples were made from local erratic boulders (transported to the Southern Baltic Lowlands during the Pleistocene glaciations from Fennoscandia), as there were no quarries in this area. Their size varies from several centimetres to over 1 metre in diameter. Based on the millstone-eye we are able to determine whether it was runner-stone or bedstone. There have also been surviving examples with furrows still visible. Many of the millstones are semi-finished pieces, unfinished for some reason at various stages of production.

This work was supported by the National Science Centre, Poland (Grant No. 2019/35/B/HS3/03933).