Petrography and provenance of sandstone from Piast Castle and its adjacent chapel in Legnica (SW Poland): implications for medieval and early modern building stone supply

Abstract

Piast Castle in Legnica (SW Poland) is one of the largest preserved Late Romanesque secular residences in Europe. Constructed and remodelled between the late 12th and 17th centuries, the Castle and its chapel incorporate numerous sandstone architectural details, the provenance and petrographic characteristics of which have been insufficiently documented. We identify the lithological types and probable sources of these sandstones, and investigate their variability in relation to distinct construction phases. A total of 26 samples of historic building stone from Piast Castle and its adjacent chapel, representing the late Romanesque, Gothic, and Renaissance phases, were compared with 24 reference samples of the Cretaceous Quader Sandstones from the North Sudetic Synclinorium. The petrographic analyses encompassed optical microscopy with subsequent grain size distribution and modal analysis, complemented by scanning electron microscopy analyses on reference material. The results of the study indicate that two sandstone types from the North Sudetic Synclinorium were used in the construction of this heritage site: the Coniacian Upper Quader Sandstone and the Turonian Middle Quader Sandstone. This petrographic variability correlates with construction phases: late Romanesque details were carved from both lithological types, whereas Gothic and Renaissance elements predominantly used Upper Quader Sandstone. The findings provide new insights into medieval and early modern material procurement strategies in the Lower Silesia historical area and deliver a petrographic framework for conservation and restoration strategies.