Seathwaite Tarn, English Lake District, Britain

Quartz-sulphide veins, worked for copper in the nineteenth century, cut Ordovician tuffs and agglomerates. The earliest assemblage of quartz, chlorite and haematite was followed by minor arsenopyrite, pyrite and cobaltite, followed by copper and copper-iron sulphides. The mineralogy and textural relationships of these ores are similar to those found in supergene-enriched ores. Oxidation is restricted to the minor development of siderite and malachite.

Major Minerals:

Digenite, djurleite, bornite, haematite

Minor Minerals:

Wittichenite, chalcopyrite, blaubleibender covelline, covelline

Trace Minerals:

Include arsenopyrite, cobaltite, pyrite, native gold


Minor arsenopyrite, pyrite and early haematite are euhedral and replaced by digenite and djurleite. Digenite is replaced along cleavage and fractures by covelline, secondary haematite and wittichenite. Djurleite and digenite are replaced along grain boundaries by bornite, wittichenite and secondary haematite. Bornite, wittichenite and digenite form graphic intergrowths. Bornite is replaced by chalcopyrite and covelline


Stanley and Criddle, 1979