The Nent Valley forms part of the Alston Block, the most Northern Block of the North Pennine Orefield. The River Nent flows for 8km from its headwaters above the village of Nenthead to its confluence with the River South Tyne near the town of Alston. The geology is composed of a sequence of cyclic Carboniferous rocks resting unconformably upon a Lower Palaeozoic basement which is intruded by Devonian Granites. Hydrothermal mineralisation of the orefield took place around 270Ma and created a series of productive veins and flats. The area has experienced over two centuries of intensive mining for lead and, later zinc ores that ended in the early 1900’s.

Over 90 adits were driven throughout the valley, presently five adits discharge metal-rich water to the River Nent. Areas of contaminated land, spoil heaps, tailings dams and stream sediments also act as sources of metal contamination. The River Nent has very limited aquatic fauna due to high aquatic and substrate zinc concentrations. The average zinc concentrations in the main river are above the Environmental Quality Standard (EQS) value for salmonid fish (0.5mg/l). At Nenthead they are also above the EQS value for coarse fish (2.0mg/l) for a river such as the Nent with total hardness between 100 and 500mg/l as CaCO3. The degradation of the River Nent is also significant due to its potential impact upon the River South Tyne, an important river both in terms of its water resources and its fisheries. The overall aims of this thesis have been to gain a better understanding of the sources and behaviour of zinc in the Nent Valley and to develop a treatment system for passively removing zinc from these circumneutral mine waters

Blagill Mine is the outstanding place in the area and is situated on the S side of Newshield Moss between The Nent and South Tyne Valleys. Although the first ancient mining here, perhaps as far back as the 14th century, was for lead, the mine became unique in the 19th century as a commercial producer of barytocalcite. When the higher barium-content witherite from nearby Nentsberry came onto the market, the demand for the inferior Blagill product dried-up and there are no production records after 1895.

The main veins worked were Slote, Thorngill-Lough, Shildwell or Whitwell and Fistas Rake or Blagill Old. Minor strings also tried were Coatley Hill and Copperbole Head veins. The site is now a SSSI and as such is supposed to be closed to collectors.