Coniston Mines and Quarries

Also within

Cumbria County LAKE DISTRICT National Park

Condition (Natural England)

Geology & landscape

Mining / Industrial: Mine Spoil · Geological Period: Devonian, Ordovician, Silurian · Rock Type: Andesite, Breccia, Rhyolite

Landscape processes: Volcanic / Igneous

Description

Description Coniston Mines and Quarries consists of two areas of fell land and crags on the north east side of the Coppermines Valley which runs between Coniston village and Levers Water is south Cumbria. The rock outcrops, mine spoil and disused mine workings provide evidence of a major volcanic episode which occurred in northern England in the Ordovician Period and of the subsequent mineralisation which took place. Excellent exposures in the eastern part of the site demonstrate the character of the mid Ordovician Borrowdale Volcanic Group in the southern Lake District. A variety of rock types are exposed, including tuffs, andesitic peperitic sills, ignimbrites and breccias produced by ancient mud flows. Of particular interest is the thick, composite welded ash flow tuff forming the cliffs of Long Crag. The volcanic rocks belong to the last phase of volcanism, which formed the Yewdale breccia, Yewdale Bedded Tuff and Wrengill Andesite. These exposures are a key site for interpretation of late Borrowdale volcanic environments. The Lake District forms a geographically well defined base metal orefield. The sulphide mineralisation occurs as vein deposits and is notably diverse in terms of both the nature of the ores and their age. The western part of the site is located on a cluster of veins running approximately south east direction from Levers Water for a distance of about 900 metres and over a width of approximately 400 metres. The veins cut obliquely across the strike of a series of tuffs, andesite and rhyolite of the Ordovician Borrowdale Volcanic Group. The two principal veins are the Bonser Vein and the Paddy End Vein. The typical mineral assemblage is quartz, chlorite, chalcopyrite, arsenopyrite, tennanite and pyrite, with abundant magnetite in the Bonser Vein. Recent studies of material from the Bonser Vein have shown that a diverse range of minerals are present including various bismuth minerals and the first British occurrence of laitakerite. Minor amounts of the cobalt and nickel arsenides 'scutterudite, var. smaltite' and 'nickeline' are reported from the veins. The site is of national importance for the diversity of primary and secondary ore minerals present in the old mine workings. The mineralisation is the best example of the Late Silurian / early Devonian, 'chalcopyrite pyrite arsenopyrite' type of mineralisation in the Lake District.