1) In some northern counties ‘delf’ was the usual word for a quarry.
1538 a stone delfe in the hyeway, Ovenden
1623 everye person who breache the Lordes soile for stone ... other than in the usuall delfe shall fill upp the same, Lepton. It was used particularly for ironstone mines and was occasionally an alternative to ‘pit’: 1575 their myne and dellff of ironstone, Emley
1608 one depe pytt or delfe just in the meddell of an hyghe way, Warley
1704 hath had severall times ... Coales stollne from his Lime delfe in Bingley. The verb occurs occasionally in coal-mining contexts: 1659 liberty to digge, delve and sinke pitts, North Bierley and the noun was an occasional alternative to coal-pit: 1677 This money is for Manageing of the Coal Delph, for Colliers must be paid, Barlborough. Note: 1665 ther was a delefe hole payned in the townshep ... sufficiently amended, Langfield.