The CSIRO Mineral Resources X-ray Technologies Group develops industrial X-ray analysis instruments for real-time measurement of elements and minerals in process stream slurries. X-ray fluorescence (XRF) is widely used in mineral processing plants to measure concentrations of precious and base metals such as gold, platinum, nickel and copper for process control and plant monitoring. However, mineralogy is often the most important physical property affecting beneficiation efficiency. CSIRO has also developed and patented specialised X-ray diffraction (XRD) technology to monitor the mineral composition of slurries directly on-stream in mineral processing plants. This approach removes the complexities associated with traditional laboratory XRD analysis of slurries and enables real-time mineralogical monitoring. The high-accuracy XRF and world-first online XRD technologies have been combined into a slurry analyser known as the Mineral and Elemental Analyser (MEA). The MEA is an autonomous, standalone unit that measures a continuous slurry flow of up to 120 L/min and reports results at intervals of 5–10 mins. The MEA has been installed in several processing plants in Australia, where it monitors elements and minerals critical for evaluating plant process performance. This paper outlines a recent field trial in which the combined XRF and XRD technologies were tested at the McArthur River Mine zinc–lead concentrator in the Northern Territory. The study had two objectives: to measure concentrations of gangue minerals, including quartz, mica and phyllosilicates, to determine the total silica (SiO₂) content of concentrate streams; and to demonstrate measurement of key elements in the process slurry. The trial demonstrated a measurement accuracy of 1.77 wt per cent (13.6 per cent relative) for total silica and showed good real-time measurement of sphalerite, galena, pyrite, Zn, Pb, Fe and Cu.