Silica rock (as quartzite) was mined underground here, following one bed over an area of 1000 yds by 500 yds (915m x 457m), the roof left supported by pillars of quartzite left standing. The rock was discovered in the 1780s and exploited thereafter and by 1807 a tramroad (Dr Bevan's) was built to take the product to the Neath Canal. In 1827 Dinas Firebrick was invented locally by WW Young, its constituents being silica with some added lime. Used as a refractory brick for lining furnaces it became world-famous. The original mines were extended by Richard, Thomas & Baldwins Ltd who manufactured firebricks at Landore, Swansea.
The mines were served by a crushing plant adjacent to the Afon Sychryd, the bases of which are still visible, a tramroad (NPRN 411296), an aerial ropeway, the silica processing plant and a powder store. The mine continued to be worked until 1964 eventually closing with the decline of the open-hearth steel process.

S.Hughes & P.Reynolds (1992) A Guide to the Industrial Archaeology of the Swansea Region, p.9-10.
Cadw scheduling details (1996)