Ironstone was mined briefly from Tyllau Mwn (nprn 527249) in 1770, and again on a more modest scale in 1878 and 1910. A deep linear open-cast working is shown on the 1890 OS map and consists of a cutting 25m long NW-SE and up to 4m wide; up to 4m deep at the uphill (SW) end. The bedrock face is visible along its length, the floor covered by thin turf over stone, possibly thrown back as infill. There are a number of spoil tips associated with this level (nprn 527290-527293).
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 13/11/2012.