St Bees Sandstone. Cumbria, Britain

This Sandstone is a Permo-Triassic feldspathic to quartzose arenite.

Major Minerals:

Haematite, rutile, anatase, zircon

Minor Minerals:

Relict magnetite, ilmenite and chromite; pyrite, chalcopyrite


Detrital iron-titanium oxides are rounded and show relict magnetite-ilmenite oxidation-exsolution textures. Most magnetite grains have been altered to martite and most ilmenite to haematite-TiO2, mixtures. Syntaxial overgrowths of haematite as lanceolate crystals on detrital haematite grains are called specularite. Rutile and anatase overgrowths on rounded TiO2, grains are common. Euhedral anatase crystals occur within pore spaces and fine-grained haematite, called pigment, coats detrital silicate grains or lie along the cleavage planes of altered phyllosilicates.


Turner and Ixer, 1977; Ixer et al., 1979b; Turner, 1981