Geography of Sheffield county, from bituminous (ideal for domestic heating) to "Thick Coal", of a semi-anthracitic quality, appropriate for use in iron-smelting and in engine furnaces. Associated with the Upper Coal Measures were valuable iron ore deposits, occurring in the form of nodules. Large quantities of locally occurring fireclay were also exploited, as well as ganister (a clay used to make refractory furnace linings). The city of Sheffield derives its name from the River Sheaf which Until the 17th century was written as "Scheth" or "Sheath". Sidney Oldall Addy equates the origins of this word with the Old English "shed" (as in "water-shed")
Sheffield indoor climbing centres. Sheffield was the UK's first National City of Sport and is now home to the English Institute of Sport – Sheffield, where British athletes trained for the 2012 Olympics. Sheffield also has close ties with snooker, with the city's Crucible Theatre being the venue for the World Snooker Championships. The English Institute of Sport hosts most of the top fencing competitions each year, including the National Championships for Seniors, Juniors (U20's) and Cadets (U17's) as well as the 2011 Senior European Fencing Championships. The English squash open is also held in the city every year. The International