Limonite, haematite and magnetite. Hamersley Basin, Australia
250µm
Two curved bands (brown-grey) comprise a fine-grained intergrowth of magnetite, haematite and limonite which cannot be distinguished from each other at this magnification. Coarse-grained, characteristically lath-shaped haematite (blue-white, centre) grows between the bands within limonite (blue-grey, top right), which is the main phase. Limonite shows faint reflection pleochroism (grey-blue to grey-brown) and bireflectance. Dark grey areas are silicates.
Polished block, plane polarized light, x 80, air
