Mineral particles are detrimental to lignocellulosic biomass utilization as fuel and feedstock of advanced biorefineries. Minerals may cause corrosion, sintering, and vitrification in boilers, gasifiers, and combustors as well as abrasion and erosion of mechanical equipment used in biomass processing. In this work, we employed synchrotron X-ray computed microtomography to analyze mineral particles in fibers of sugar cane bagasse, the vast lignocellulosic residue of the sugar cane industry. Hundreds of mineral particles with volumes from similar to 10(2) to 10(4) mu m(3) were observed and analyzed. Mineral particles were found mostly in three regions of the biomass particles: (i) at external surfaces, (ii) at internal surfaces associated with tissue cracks, and (iii) inside parenchyma cells, which were ruptured for extraction of the sugar-rich juice. These results provide novel insights for the development of bagasse cleaning technologies aiming at improving feedstock quality for combustion and biorefining.