1) Could refer to places where charcoal was burned, but often context makes it clear that they were also places where coal was mined.
The term ‘coal-pit’ poses problems similar to those of ‘coal’ and ‘collier’ for it could refer in the past to places where charcoal was burned. These sites had a variety of names: 1527 Turves and hillinges to cover his Charcole pittes, Kirkheaton
1672 libertye to burne the same into coale … and to sett Coalepitts and get sods, Turfes and Dust, Tong
1763 leive to ... make charcoal pitts, Esholt
1795 and make pit steads for Coaling the same, Calverley. In some early references there might be ambiguity but often the context makes it clear that the coal-pits were places where coal was being mined: 1323 ‘stole cattle and slaughtered them in le Colepittes’, Wakefield
1497 via usque colepittes de Shelf. A coroner's report of 1357 records the death of a Lepton man who fell into a colpyte. A Bradford lease has: 1659 pitts or mynes of Coales, North Bierley. The modern dialect pronunciation is evident in spellings from the early sixteenth century: 1502 I wyll that Edward Robertschaw have half a coile pytt of Clayton dewring oon yere.