Magnetite, calcian rhodochrosite, limonite and chalcopyrite. Harlech Dome, Wales, Britain




Click here



500µm


Euhedral magnetite (brown, top left) crystals occur within a matrix of calcian rhodochrosite (light grey, faint bireflectance). Microconcretions of calcian rhodochrosite are replaced by fine-grained iron hydroxides/manganese oxides (blue-brown-grey, centre right) in a matrix of unreplaced calcian rhodochrosite. A veinlet of limonite (blue-grey, top) crosscuts the primary banding which is oriented left-right. A single crystal of chalcopyrite (yellow, centre bottom) illustrates the low reflectance of the other phases. Black areas are polishing pits.


Polished block, plane polarized light, x 40, air



Click here for Associations Click here for Mineralogy Click here for high-res image (~300K)