A review of the mineralisation at Driggith and Sandbed mines, Caldbeck Fells, Cumbria

Abstract

Low temperature lead-zinc-copper veins are developed within a NE-SW trending fracture system in rocks of the Eycott Volcanic Group at Driggith and Sandbed mines in the Caldbeck Fells, Cumbria. The lead veins were worked by a succession of mining companies from the 18th century onward, first at Driggith mine and later at Sandbed mine. East-west trending baryte-quartz-carbonate veins were worked for baryte in the mid-20th century. The dumps from these mines surround and in some cases cover those of the earlier lead workings. Several episodes of primary mineralisation can be distinguished. The primary lead vein mineralisation comprises major quartz, calcite, sphalerite, galena and chalcopyrite. Sparse antimony-rich sulphide mineralisation is present as inclusions in the galena. There is rich, localised, iron sulphide-arsenopyrite mineralisation, which pre-dates the lead-copper-zinc vein mineralisation; sparse nickel- and cobalt-bearing mineralisation of unknown affinity, and baryte mineralisation with quartz and carbonates that post-dates the lead-copper-zinc vein mineralisation. The later baryte is present in distinct E-W trending veins and as a later stage of mineralisation in the fractures that host the lead-copper-zinc vein mineralisation. Supergene oxidation is extensive. About sixty supergene minerals have been identified. Distinctive specimens of curved green arsenate-rich pyromorphite on hackly quartz are well known from the opencut above Driggith mine. Bayldonite, cerussite, mimetite and malachite are widespread and abundant. Anglesite, aurichalcite, hemimorphite, Iinarite and philipsburgite are relatively common in micro-crystalline specimens. The arsenate minerals bariumpharmacosiderite, beudantite, mimetite, segnitite and scorodite form distinct localised gossans, which are closely associated with primary arsenopyrite. A variety of sulphate minerals including brochantite, langite, linarite, serpierite and schulenbergite have been formed by post-mining oxidation. Minerals discovered for the first time at the Sand bed and Driggith mines as a result of this study include arsendescloizite, annabergite, brianyoungite, djurleite, erythrite, gersdorffite, kottigite, lanarkite, lavendulan, olivenite, mawbyite, parnauite, philipsburgite, pyrrhotite, redgillite, strashimirite, yarrowite and zalesiite. Of these, annabergite, brianyoungite, gersdorffite, lavendulan, parnauite, strashimirite, yarrowite and zalesiite are reported for the first time in the Caldbeck Fells and mawbyite for the first time in the British Isles. The published mineralogy of the Driggith and Sandbed mines is complicated by the claims of Arthur Kingsbury, many of which are fraudulent. Rare species claimed by Kingsbury, which should be removed from the list of minerals from Driggith and Sand bed include allophane, chalcanthite, conichalcite, chlorargyrite, plancheite, plumbogummite, phosgenite, pseudomalachite, turquoise and wulfenite. In addition, many fine specimens in the Kingsbury collection which are labelled from Driggith or Sandbed mine, including common species such as adamite, brochantite, cerussite, leadhillite, Iinarite and malachite, are fraudulent, although undoubted specimens (almost always of much poorer quality) are well known at both localities