Red bed copper-lead-zinc mineralization




Galena, sphalerite and covelline. Alderley Edge, Cheshire, Britain


Click hereGalena (white, centre) has characteristic triangular pits due to plucking along the (100) cleavage. Sphalerite (light grey, centre top) is euhedral to subhedral and intergrown with galena. Minor amounts of covelline (deep blue, centre right) are associated with the alteration of galena and show its original grain size. Quartz crystals (dark grey, left, top) have euhedral terminations. Smaller euhedral quartz crystals (centre right) within galena show strong internal reflections. A rock clast (dark grey, bottom right) occurs within pitted coarse grained baryte (medium grey, bottom). Black areas arc polishing pits.



Polished block. plane polarized light, x 80, air


Galena and pyrite. Alderley Edge, Cheshire, Britain


Click hereGalena (white, bottom right) cements quartz (dark grey, well polished, right) and feldspar (dark grey, less well polished, centre). An aggregate of small pyrite (yellow-white, centre top) crystals occurs between two feldspars. The larger feldspar (centre left) is euhedral and is partially authigenic in origin. Black areas are polishing pits.



Polished block. plane polarized light, x 80, air


Sphalerite and galena. Alderley Edge, Cheshire, Britain


Click hereGalena (white, top left) and sphalerite (light grey, centre top) are the main sulphides cementing the quartz grains (dark grey). Sphalerite has a thin discontinuous galena veinlet within it. Dark areas (right centre) arc polishing pits infilled with ¼śm diamond paste which gives diffuse light-coloured internal reflections.



Polished block, plane polarized light. x80, air


Chalcopyrite, sphalerite, galena and covelline. Alderley Edge, Cheshire, Britain


Click hereChalcopyrite (yellow, bottom) cements and replaces quartz (dark grey, centre top) and is itself replaced by covelline (deep blue, centre top left). Sphalerite (light grey, centre left, top centre) occurs about the margin of chalcopyrite. Galena (white, bottom left) also cements the silicates. Black areas are polishing pits.



Polished block, plane polarized light, x 80, air


Chalcopyrite, sphalerite and covelline. Alderley Edge, Cheshire, Britain


Click hereChalcopyrite (yellow, centre top) is the main cement and is altered along its edges to covelline (deep blue, centre left) and limonite (medium grey, centre top). Sphalerite (light grey, centre top, centre left) occurs as small inclusions within chalcopyrite. Quartz (dark grey) and feldspar (dark grey with cleavage, bottom left, bottom right) show faint light-coloured internal reflections. Black areas are polishing pits.



Polished block, plane polarized light, x80, air


Djurleite and cerussite. Alderley Edge, Cheshire, Britain


Click hereRhythmically banded djurleite (blue, centre) and cerussite (light grey, centre) infill void-space between detrital quartz grains (grey). Authigenic quartz overgrowths are visible giving euhedral terminations to the quartz (left centre). The junction between original elastic grains and their overgrowths is marked by a fine line of voids or 'dust' (top left, centre top right).



Polished thin section, plane polarized light, x 80, air