 Close to the village and gorge are Batts Combe quarry and Callow Rock quarry , two of the active Quarries of the Mendip Hills where limestone is still extracted . Operating since the early 20th century , Batts Combe is owned and operated by Hanson Aggregates . The output in 2005 was around 4 @,@ 000 tonnes of limestone per day , one third of which was supplied to an on @-@ site lime kiln , which closed in 2009 ; the remainder was sold as coated or dusted aggregates . The limestone at this site is close to 99 percent carbonate of calcium and magnesium ( dolomite ) . 
