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TEACHING EARTH SCIENCES ● Volume 30 ● Number 1, 2005 Collecting minerals Headgear above George’s shaft clearly fault breccia, the angular fragments of the host Mytton Flags Formation are cemented by the minerals .Students should recognise a structural control of the mineralization with faults acting as lines of weakness, and channels along which mineralizing solutions migrate. The intensity of faulting of the Shelve Inlier is considerable. The inlier is bounded to the east by the Pontesford Lineament (Woodcock 1984) and is dominated by strike-slip duplex systems associated with the Welsh Borderland Fault System (Lynas 1988). The discussion on controls of mineralization could be extended by visiting the well-known Stiperstones ridge, 4 kilometres south of Snailbeach. Parking is available at the site of the Bog mine (SO357978) or next to the minor road (SO369976) to Bridges (Allbutt, Moseley, Rayner and Toghill 2002). The Stiperstones Quartzite Formation intriguingly doubles up as a barrier to the mineralizing fluids that precipitated the primary baritesulphide deposits, but also acts as a recipient to very small scale secondary deposits.Underground workings, now inaccessible, show that the barite-sulphide veins die out at the top of the Stiperstones Quartzite (Dines 1958), while traces of hematite, malachite, azurite and bornite have been found staining fractures in this unit 100 metres south (SO367985) of Manstone Rock (Moseley 1994). Students reasonably suggest that the secondary copper minerals were most probably derived from the weathering of the small amounts of chalcopyrite in the overlying barite-sulphide deposits. The origin of the hematite may be quite different. Silica rich rocks in south Shropshire show evidence of hematization. This is possibly attributable to a former Permo-Triassic redbed cover. The susceptibility of limestones to mineralization is mentioned above, but with the tendency of some sandstones to be mineralised, this raises the possibility in certain areas of mineralogically more simple rocks being preferentially mineralised. Are there other examples of this trend In Charnwood Forest, Leicestershire the Precambrian Charnian Supergroup is overlain by red Triassic breccias and sandstones The more silicic Charnian rocks, quartz-arenite sandstones and rhyolitic volcanics are hematised, less acidic volcanics, pelites and immature sandstones are not. 6 Mining and mineral processing At Snailbeach levels were driven from a main shaft. Winzes, which are underground shafts, were developed from the levels. Ore, won from stopes, was carried along the levels in wagons, and winched to the surface in large wrought iron barrels called kibbles. Drainage problems in the Shelve mines were overcome by digging horizontal adits. Having recognised earlier the contrasting densities of gangue and economic minerals students should appreciate the significance of this property in the separation processes. After fine crushing separation utilised buddles and jiggers to wash away less dense gangue material. This left the more dense galena as the concentrate ready for smelting. 7 History Providing time is available a look at the historical development of a mine is always worthwhile. Snailbeach mine boasts a fascinating history (Brook and Allbutt 1973) Lead mining started in Roman times, peaked in the 1850’s and finally ceased in 1911. Barite extraction con- www.esta-uk.org 16
TEACHING EARTH SCIENCES ● Volume 30 ● Number 1, 2005 tinued until 1955. From 1863-1895 a smelt mill operated at Snailbeach, and a narrow gauge railway ran from the mine, to transport smelted lead, and after 1895 lead ore to the railhead at Minsterley. The Snailbeach site was reclaimed by Wardell Armstrong Ltd. during 1993 and 1994 which included disposal of tips of white smelt waste. Although this and other sites are now safe visitors to the area should be aware that shafts and open adits still exist and appropriate care should always be taken. 8 Further details of the Snailbeach Mine site The Snailbeach Mine site is managed by Shropshire Mines Trust on behalf of Shropshire County Councils Countryside Services, and has an Interpretation Centre, which gives an excellent insight into the lead mining industry in south Shropshire. For more information,including booking parties for surface and underground tours visit the Snailbeach website on www.ap.pwp.blueyonder.co.uk/sbeach/sbeach.htm. John Moseley Dingle Nook, Shirley Lane Longton, Preston PR4 5NJ john@dinglenook.freeserve.co.uk References Allbutt, M., Moseley, J., Rayner, C.& Toghill, P. (2002) The Geology of South Shropshire. Geologist’s <strong>Association</strong> Guide. 27, pp. 116. Brook, F.& Allbutt, M. (1973) The Shropshire Lead Mines. pp. 92. Moorland Pub., Staffs. Dines, G. G. (1958) The West Shropshire Mining Region Bulletin of the Geological Survey of Great Britain. 14, pp. 1-43. Lynas, B.D.T. (1988) Evidence for dextral oblique-slip faulting in the Shelve Ordovician Inlier, Welsh Borderland: implications for the south British Caledonides. Geological Journal, 23, pp.39-57. Moseley, J. (1994) The Origin and Significance of the Hematisation of Silicic Rocks of Precambrian and Ordovician age in South Shropshire. Mercian Geologist. 13(3), pp. 111-115. Pattrick, R.A.D.& Bowell, J.R.(1991). The genesis of the West Shropshire Orefield: evidence from fluid inclusions, sphalerite chemistry, and sulphur isotope ratios. Geological Journal. 26, pp.101-115. Toghill, P. (1990) Geology in Shropshire. Swan Hill Press, Airlife Publishing, Shrewsbury. pp. 188. Woodcock, N.H. (1984) The Pontesford Lineament, Welsh Borderland. Quarterly Journal of the Geological Society of London. 141, pp. 1001-1014. Top: Locomotive shed Bottom: Compression engine House 17 www.esta-uk.org
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