Pyrite and TiO2 mineral, Lancashire, Britain
An argillaceous limestone in which pyrite is poorly crystalline and porous (light yellow, centre), or well crystalline and euhedral (centre top) or replaces fossil fragments (left). Poorly crystalline TiO2 (blue-grey, centre) is probably anatase. Calcite (dark grey, well polished) and clay minerals (darker grey, poorly polished) are the main matrix phases. The sulphides and TiO2 mineral are associated with coarse-grained calcite, rather than the fine-grained matrix carbonate.
Polished block, plane polarized light, x 80, air