Slab Mill for Gorseddau Quarry.****

This cathedral-like structure has been conserved by Snowdonia National Park and comprises two main floors, an attic that may have served as storage, and a partial basement that possibly functioned as a workshop. An internal pit housed a large breast-shot wheel, accompanied by a deep shaft trench that extended outside to facilitate shaft maintenance. A fine water tunnel and traceable leat run from Llyn Cwmystradllyn, while tramway formations on both ground and upper floors connected to the Gorseddau tramway. The upper floor was likely used for light woodwork and assembly, while the ground floor accommodated heavier machine work. Nearby Prenteg turning retains a length of multi fish-belly rail, possibly from the original tramway.

The mill was built in the mid-1850s as a slab mill for Gorseddau quarry but had fallen idle by the late 1860s, later seeing occasional use as a public hall. Its design followed mid-Victorian industrial patterns and resembled buildings such as the Cannons Road Gasworks in Bristol. Output was trifling, consisting mainly of saws, planers, and polishers, with hand-finished writing slate frames possibly produced on the upper floor.