Portable Low-Impact Surface Hardness Testing of Mineral Materials: An Integrative Review of Applications, Interpretation, and Methodological Considerations

This integrative review critically examines portable dynamic Low-Impact Surface Hardness (LISH) testing, also known as Leeb hardness. Since its adaptation for mineral materials in 1993, LISH has been increasingly adopted across geoscience, engineering, and heritage conservation as a portable, minimally invasive alternative or complementary method to traditional methods such as the Schmidt Hammer. Despite this increased use, methodological knowledge remains fragmented across disciplines, with operational limitations and data interpretation challenges frequently underreported. To address this, this review combined a semi-systematic literature review (n = 181 publications) with a cross-and interdisciplinary user survey (n = 50) to identify key strengths, including utility, versatility, and suitability for weathering and conservation assessments, while critically addressing challenges related to surface heterogeneity and porosity, as well as calibration and standardisation. Furthermore, this review identifies opportunities to extend the use of LISH to heterogeneous and layered materials, surface-biological interactions, and more systematic integration within existing monitoring frameworks. The review encourages transparent reporting of protocols, integration within multi-analytical frameworks, and the development of standardised procedures to enhance cross-study comparability and support informed adoption across research and practice.