Nationally important remains of Mona Mine (nprn 300167) calcining kilns and sublimation chambers are now craters and stone structures respectively set in an area of waste, some 280m east-west by 80m, to the south of the precipitation pits (nprn 33753). The area also includes a detached sublimation chamber at the west end and a circular-walled, roofless, explosives magazine. Calcining and sulphur sublimation was practised from before 1785 at Mona and was carried out by roasting ore in heaps to remove sulphur and other impurities.
(Source: Cadw scheduling description)
B.A.Malaws, RCAHMW, 02 February 2007.