In Australia, almost 1 billion tonnes of Iron Ores were produced in 2018. This represents about half of the total value in mineral exports for the Australian economy. The vast majority (around 96%) of the iron ore is mined from deposits located in the Hamersley province of Western Australia and are associated with the Archean Marra Mamba iron formation and the Proterozoic Dales Gorge member. Ongoing weathering processes affect variably these ores and continuously modify their original properties which in turn affect ore quality and inevitably selling price. The quality of an iron ore deposit is directly related to their geometallurgical properties and Fe contents and it is ultimately controlled by mineralogical, chemical and textural (3D distribution of pores and minerals and their shape/association characteristics) parameters. In this contribution, we present a workflow combining high-resolution X-ray computed tomography with high-resolution scanning electron microscopy and image processing to provide new insights into the fine microstructure of Australian Iron Ore. Our study focus on the nano- to millimetre scale characterisation of ochreous goethite with implication for ore quality and for the assessments of the fluids pathways and their role in the potential redistribution of deleterious elements Al, Si, P, S, Se, or Co. CITATION:Godel, B, Ramanaidou, E and Verrall, M, 2019. 3D characterisation of iron ores: imaging the invisible?, in Proceedings Iron Ore 2019, pp 306311 (The Australasian Institute of Mining and Metallurgy: Melbourne).