The primary ore mineralogy of the Alderley Edge deposit, Cheshire.

In this deposit (M.A. 17-269, 466) Cu and Pb minerals occur in coarse-grained Triassic sandstones and belong to the red-bed type of mineralization. The earliest opaque phases are associated with the diagenesis of the sandstones and include authigenic anatase, plus bravoite, pyrite, chalcopyrite, sphalerite and galena; with minor Ni-Co-Fe sulpharsenides, marcasite, and tetrahedrite cementing the clastic grains. This primary assemblage has undergone alteration resulting in the formation of djurleite, covellite, and blaubleibender covellite accompanied by Pb and Zn carbonates and sulphates. Electron probe results show the pyrite to contain significant amounts of Ni and Cu (but lesser Co), the sphalerite to be an Fe-poor variety but to contain Cd (0.76-4.52%) and the chalcopyrite to contain Sb (0.18-0.97%). Chalcopyrite alters to an idaite-like phase and finally to djurleite (with Ag 0.46-2.35%). -R.A.H.