Provenance, durability and damage analysis of natural building stones by means of petrographical techniques

Several case studies taken from Belgium clearly illustrate the role and importance of optical microscopic investigation in provenance studies, quality control and damage analysis of both historical and modem natural building stones. The provenance of particular "exotic" historical building stones, such as the sandstone ashlars used in the former Roman town of Tongeren, has beeen unravelled thanks to a comparative petrographical analysis. Furthermore, the probable mechanism of frost-damaged and sulfate-attacked calcareous sandstone (the Balegern or Lede Stone) in the Beguinage of Mechelen, has been elucidated thanks to the use of high-quality thin sections and optical microscopic techniques. Finally, a combination of optical microscopic and back-scattering electron microscopic analysis, revealed the origin and processes leading to the un-aesthetic brown staining of modem limestone curbstones, the so-called bluestones.