Haematite, gibbsite, boehmite and TiO2 mineral. Gove, Northern Territories, Australia
An angular haematitized clast comprises banded haematite (white, centre left) with variations in reflectance that are related to grain size and crystallinity of the haematite. The dark brown-grey matrix is a mixture of gibbsite and boehmite. All three minerals were confirmed by X-ray diffraction. A single rounded grain of a TiO2 mineral (white, highest reflectance, centre left) lies close to a polishing pit (black).
Polished block, plane polarized light, x 40, air