We are studying the geological characteristics of the granite-gneiss that was quarried from beneath Cambrian sandstone at Lugnås for millstone production over a period of many centuries. While there is literature covering the social and industrial history of those mines, geological reasons for why this rock was well suited to millstone production have been less explored. The quarried rock is special because it appears to have undergone some unusual chemical weathering through reaction with water, which meant that it could be cut into millstones but also remained strong enough that it did not wear too quickly as a millstone.
Rock cores have been extracted, which are currently undergoing chemical and mechanical testing, and it is planned to use the new synchrotron facility in Lund, MaxIV, to help understand the unusual chemical weathering processes. Analyses are expected to be completed during 2021 and the project is a cooperation between The Geological Survey of Sweden, Stockholm University, Lund University, Linneas University and The Geological Survey of Norway.