Iron ore deposits are widespread in Britain, the main types being carbonate, haematite and limonite whose incidence is discussed by Tylecote (1962, 175–179). Quarrying with trenches as well as tunnelling is known from the Forest of Dean (Schubert 1957, 123, pls XIII-XIV) but widely occurring bell-pits are more frequent evidence of medieval deep mining of iron ore (Tylecote 1962, 284–285; Beresford and St Joseph 1979, 256, fig 107). Bell-pits near Sedgeley, West Midlands, had 1.5m diameter openings, a depth of 4.6m to 6.1m, and a maximum diameter of 3.6m.