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 largest of the workings is a irregular-shaped quarry pit approximately 80m N-S x 70m and up to 30m deep. It represents the enlargement and opening up of two earlier underground workings (nprn 527505, 527508).
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 19/12/2012.