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 mine probably belongs to one of the earlier phases of working as it is detached from the main tramway and incline systems associated with the intensive period of activity. The mine entrance is 1.7m wide and 1.7m high, but the floor becomes lower inside, and is progressively covered in silt and water. The entrance is approached by a cutting through the rock, running SE-NW but curved, 12m long, 6m wide and 6m deep. The mine itself runs N and may join up with the cavernous pit inside a small quarry (NPRN527490) to the NE.
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 19/12/2012.