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 There are six areas within the city that are designated as sites of special scientific interest. The present city boundaries were set in 1974 (with slight modification in 1994), when the former county borough of Sheffield merged with Stocksbridge Urban District and two parishes from the Wortley Rural District. This area includes a significant part of the countryside surrounding the main urban region. Roughly a third of Sheffield lies in the Peak District National Park. No other English city had parts of a national park within its boundary, until the creation in March 2010 of the South Downs National Park,