Advanced microscopy probes for geomaterials – Current state of the art and future perspectives

Geomaterials form the basis of our planet. With structural features spanning from the nanometre- to the continental-scale, geomaterials possess a complex but fascinating hierarchical structure that allows us to investigate their formation’s associated physical, chemical, and biological processes. Geomaterials provide us insights into the formation and evolution of the Earth as well as the origin of life as preserved in fossilised remains of microorganisms. Microscopy is perhaps the most powerful tool that helps us to appreciate and understand geomaterials. With rapid advances in experimental science during the last several decades, we can now image internal structures and follow internal dynamic processes in real-time in three dimensions (3D). A wide range of current 3D imaging methodologies have emerged that help us understand and observe geomaterials’ relevant structural features. Attenuation-based 3D X-ray tomography is the most used micro-scale technique, which can be paired with complementary techniques to highlight more features and details within geomaterials. This review documents the relevant complementary microscopy modalities: phase contrast and diffraction contrast X-ray tomography, neutron tomography and electron tomography, and other methods like atom probe tomography and chemical- and structural-specific Raman imaging. This review article aims to provide an overview of a wide range of microscopy methodologies (for researchers) and the insight that can be garnered from their use with geomaterials.