Handheld X-Ray Fluorescence Analysis (HH-XRF): a non-destructive tool for distinguishing sandstones in historic structures

Determining the provenance of building stone can be important when researching the history of historic structures or identifying suitable substitute stone to use in building repairs. Commonly, however, there is no written record of stone source, and a visual examination alone is inconclusive. In many such situations stone provenance can only be constrained with confidence if the stone has a distinctive property or character that allows it to be distinguished from, or matched with, other stones. A small proportion of stones have one or more genuinely distinctive visual characteristics that uniquely confirm their provenance, but for most stones such distinctive properties, if they exist at all, are cryptic and usually revealed only by microscope examination or bulk chemical analysis. However, collecting and analysing representative hand samples for this purpose can be difficult, timeconsuming and damaging to historic structures. Handheld X-Ray Fluorescence analysis offers the potential to provide bulk composition data without the need to collect physical samples. HH-XRF instruments are lightweight, wireless and portable, and they provide a rapid, non-destructive means of analysing most materials in a wide range of settings. This study has examined the benefits and limitations of the instrument when applied to sandstone building stones from the UK. A programme of laboratory tests has been used to: develop a robust methodology for gathering, managing, displaying and interpreting data; determining the extent to which sample surface condition affects the analytical results; and assessing the degree to which different sandstones can be distinguished on the basis of their bulk composition. The results are promising: the data can be used to compare, distinguish and match visually indistinguishable sandstones (and potentially a wide range of other geological and man-made materials) quickly and easily, and as such the method should find widespread application in disciplines such as building conservation and archaeology.