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TEACHING EARTH SCIENCES ● Volume 30 ● Number 1, 2005 Visiting Abandoned Mines Old mine workings are a common feature in parts of upland Britain. Some, such as those deep in the Aran Mountains of north Wales, are in very remote places, and sometimes only traces of workings remain. Other disused mines, for instance Snailbeach in the Ordovician Shelve Inlier and Llangynog on the southern edge of the Berwyn Mountains are far more accessible. Care should always be taken when visiting these abandoned industrial locations, although many sites have been made safe by local county councils, Forest Enterprise and private owners. Some mines are open to the public, and Clearwell Caves, a source of iron ore in the Forest of Dean, the Llywernog silver – lead mine, near Aberystwyth, and the Sygun copper mine at Beddgelert are some examples of those worthy of a visit. These fascinating locations are a valuable educational facility for all academic levels, providing rich geological material and items of archaeological interest. JOHN MOSELEY Left: Model of Snailbeach Mine in the interpretation centre. Right: The entry to Snailbeach Mine Why visit old mines Mineral veins are rarely well exposed in the field and not usually accessible for examination in working mines, or derelict mines sealed for safety. Spoil tips provide this vein material for examination. The enjoyment of searching out good mineral samples is an occupation that appeals to most ages. For primary age children especially the fun of collecting good specimens of attractive minerals in an organised way can be the trigger for a life long interest in earth sciences. An ideal safe site to search for minerals is the reclaimed Snailbeach Mine (Figure 1, SJ373022) 17 kilometres southwest of Shrewsbury on the eastern section of the Shelve baritesulphide orefield (Figure 2). For many years I used the Snailbeach, and adjacent Pennerley (SO353988) and Myttonsbeach mine (SJ368000) sites, as part of A-level residential fieldwork in south Shropshire. Rather than allowing visits to mine sites simply to become a hunt for minerals, I developed the following observation and discussion pathway. This can be applied to any safe site with accessible spoil material. 1 Collection and identification of economic and gangue minerals and the host rock The Snailbeach spoil tip yields excellent specimens of quartz, barite, calcite, sphalerite and galena, as well as small amounts of pyrite, chalcopyrite and malachite, while cerrusite, calamine and pyromorphite have also been reported (Toghill 1990). A-level or undergraduate students collect and identify minerals utilising the diagnostic criteria of cleavage, streak, density and crystal form. Sphalerite, galena and barite were the main economic minerals. The host or country rock for the Shelve barite-sulphide orefield is the Ordovician Mytton Flags Formation, that comprises shales, mudstones, siltstones and greywacke sandstones. The Snailbeach www.esta-uk.org 14
TEACHING EARTH SCIENCES ● Volume 30 ● Number 1, 2005 vein material reveals angular fragments of host rock strongly cemented by the main minerals listed above. This suggests mineralized fault breccia. The structural control of mineralization is discussed later. 2 Crystallography The Snailbeach spoil tip provides mineral specimens that show good crystal development, especially cubic galena and hexagonal quartz crystals, the latter displaying hexagonal columns and pyramids. These are an excellent aid to enhance the understanding of crystallographic principles. A good crystal specimen collected in the field is a far more stimulating way of investigating interfacial angles and crystallographic axes than examining plastic models in the laboratory. Maybe crystallography isn’t so bad after all! 3 Abundance of essential metallic elements After students have collected specimens of economic minerals emphasise how many important metals make up only a trace (
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