15 No matter what resource is being extracted the process of modern mining is highly automated and technologically advanced Today sophisticated machinery is critical to mining For both coal and miner als mining is usually accomplished by surf ac e or underground mining techniques The type of technique used depends on several factors including resource type location and the surrounding geology O ther types of miner als mining include quarrying a type of surf ac e mining in which large blocks of rock are mined intact or the rock itself is the intended fnal product G ranite limestone marble and sandstone are often mined this way Placer mining is used to recover precious materials such as gold or platinum from sand or gravel in streambeds S and and gravel are mixed with water and swirled or shaken so that the valuable heavy metals sink and the relatively lightweight sand stays on top to be washed away Gold panning is a simple f orm of placer mining that is enjo y ed b y r ecr e ational miner s Another method is the Frasch process currently in use in sulfur mines in the Gulf of Mexico In this process hot water is injected into a native sulfur deposit that is melted underground and brought to the surface by compressed air C oal seams deeper than 200 feet below the surface a re t ypically mined by underground methods Deposits at a shallo w er depth are extracted by surface mining which accounts for 63 per c ent of US coal production Underground coal mining is usually one of four types L ongwall accounts for 5 5 percent of underground mine production The longwall miner is a machine with a rotating drum that moves mechanically back and forth across a wide coal seam C ontinuous also kno wn as room and pillar mining this method accounts for most of the remaining underground production U tilizing a special cutting machine coal is removed from a seam and automatically transported by conveyor to the mine mouth C onventional one of the oldest but increasingly less common meth ods of mining coal uses explosives to break up a coal bed S hortwall accounts for less than 1 percent of underground produc tion This method uses a continuous mining machine in a longwall lik e method to mine smaller f ac es than are mined in longwall mining US C oal P r oduction 2008 20 18 million shor t t ons Y ear T otal C oal P r oduction 2008 1 17 18 2009 1 0 7 4 9 2010 1 084 4 2011 1 09 5 6 20 12 1 0 165 2013 9848 2014 1 0 0 00 20 15 8 96 9 20 16 7 28 4 20 17 77 4 6 2018 7 56 2 PR ODUC TION and PREP ARA TION Mining methods EIA Dr agline controls at a W y oming c oal mine