Minllyn is a slate and slab quarry (nprn 310049) begun in the C19, the most productive phase of which began after the Carlyle Slate & Slab Company was formed in 1872. Work ceased in 1924. The large slate processing mill was built in 1845. It is now roofless, is oriented WSW-ENE, 40m long, 11.5m wide at the E end, and 13m wide at the W end. The walls stand up to 2.5m high and are of dry, well-coursed slate. There are entrances in each end wall, and 2 in the S wall. Internally, against the N wall, are a series of stub walls at right-angles, to buttress against the steeply rising ground behind.
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 14/12/2012.