Magnetite, ilmenite and haematite. New Zealand
A river placer containing euhedral magnetite (brown) that has a slightly deeper colour than an irregular grain of ilmenite (brown, top left). The central magnetite crystals have oxidized to haematite. Blue-white haematite forms a rim around unaltered magnetite (centre right) but also forms martite (white, centre left) with relict magnetite (brown). The crystallographic control of the haematite oxidation along (111) planes of the original magnetite is clearly seen.
Grain mount, plane polarized light, x 180, oil