Large open pit. Used Fron Tramway.

The site is dominated by a flooded pit, representing the main working. Surviving structural remains include vestiges of a pumping-engine house, traces of pump-rod runs, ruins of a large mill and associated winding houses, and anchorages for both the chain incline and a Blondin aerial ropeway. The original short incline to the 1868 Fron tramway is still visible, crossing a notable primitive stone bridge, with the line of the tramway continuing as a verge beside the lane descending to Fron village. At the northern end of the quarry, the degraded bed of the upper pitch of the later exit incline, with steps alongside, leads down to a lower working area where there are signs of secondary excavation by tip contractors.

Twll Braich Quarry began as an open pit in the early 19th century. From 1868 onwards, it underwent major development, including construction of a steam-driven mill. Steam power also operated the chain incline and supplemented the water-powered pump. The quarry worked with one De Winton locomotive and initially used the 1868 Fron tramway before gaining a direct connection to Drumhead in the 1870s. Recorded output in 1882 reached 2,614 tons with 124 men employed. The quarry closed in 1911.