Diffraction methods in the characterization of new mineral species

Abstract

Data from publications describing new minerals in the periods 2001–2005 and 2016–2020 have been analysed to evaluate the contributions of diffraction methods to the new mineral characterisations. The two periods were chosen to be on either side of a sudden increase in new mineral descriptions from ∼50 to 120 per year and coincidentally correspond to the changeover from the majority (60%) of the new descriptions using photographic film cameras to record the powder diffraction patterns of the minerals, to using modern diffractometers. During both periods, diffraction data obtained using laboratory-based single-crystal diffractometers accounted for almost three-quarters of the crystallographic studies. Modern diffractometers can now routinely be used to collect high-quality data on crystals down to a few μm in size, once the province of synchrotrons. Large facility-based diffraction centres like synchrotrons and scientific nuclear reactors account for less than 10% of the new mineral publications. The review focuses on diffraction methods for the characterisation of fine-grained minerals, with sub-μm sized crystals. Transmission electron microscopy/electron diffraction methods are important for these cases, with an exponential increase in 3D ED methods during the last 15 years and increased usage of electron back-scattered diffraction methods for micro-inclusion minerals, especially in meteorites.