A petrographical atlas as a decision-tool in replacement and substitution of ornamental stones in historical buildings and monuments

Abstract

In addition to macroscopic analysis, microscopical study of ornamental stones in thin section leads to proper identification of the nature of rocks formerly used in historic buildings or considered for restoration purposes. Moreover, it enables the diagnosis and prediction of the weathering behavior of various rocks. Consequently, the microscopical technique is of particular interest for selecting alternative rock types as the most appropriate substitution material, especially if the original stone is no longer available or is too sensitive to weathering. In this scope, the first petrographical atlas of common natural building stones from Wallonia (southern Belgium) has been produced. The ornamental stones studied are representative of most of the sedimentary rocks found in buildings and monuments belonging to the Wallonian cultural heritage. Recent case studies dealing with the restoration of historic church facades demonstrate that the petrographical atlas serves as a good decision-making tool when selecting the most appropriate replacement or substitution material. Moreover, such a petrographical reference work is particularly useful in regions where the rocks used for ornamental purposes display varying lithological properties.