Haematite and TiO2 minerals. St Bees Sandstone. Cumbria, Britain




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125µm


This is the same area as previous section but in partially crossed polars. Coarse-grained haematite shows anisotropy (blue-white to white, bottom centre, top left). The characteristic orientation of haematite as laths along (1 I 1) of the original magnetite, so forming martite, can be seen (bottom centre). The red internal reflections of haematite are enhanced (right centre) and light-coloured internal reflections of TiO2 (white to yellow) also are present (top right). The multiple nature of the detrital TiO2 grain and its overgrowths is clear (top right). The light-coloured internal reflections of TiO2 minerals allow them to be distinguished easily from haematite in crossed polars.


Grain mount, plane polarized light, x 160, oil



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