Small underground operation.**

Several buildings in active use or good condition, including the former office, now a dwelling and still displaying the characteristic Parc ridging. The river is extensively spanned by massive slate slabs, effectively creating a culvert. At the northeastern end stands the raised Specials mill with wheel pit and slate-bedded incline flanked by stone steps, possibly powered by the mill wheel. Inside is the base of a later air-compressor installation surrounded by ridge offcuts. Opposite lies the collapsed adit with nearby lavatories and ruins of the main mill, powered by a launder from the upper wheel tailrace. The original leat serving the mill before the Specials mill construction remains traceable. Extensive rubbish runs mark the site, though the tramway branch is largely untraceable apart from traces of drum house. Above the road is a blocked adit, possibly Floor A, that appears to have functioned solely for rubbish disposal.

Emerged as a compact underground slate quarry in a narrow valley around 1870, initially worked by up to 50 men. Under Moses Kellow’s management, the operation underwent significant innovation and modernization. Had his attention not shifted to Croesor in 1895, the quarry’s development would likely have continued. The quarry closed in 1920.

The workings extended across multiple levels with considerable sophistication. Two floors above the adit (A and B) were worked southwards, while four floors below (D through G) were worked primarily northwards, with Floor D serving both directions. Floor C, at adit level, contained the main access route. Floor E, F, and G extended northwards, and an ambitious plan to drive a 700-yard tunnel eastwards from Floor F to Hafoty was never completed. Floor H remained unworked. An 80-horsepower hydraulic engine powered the H to C underground incline.

Hydraulic power drove the Kellow drills and injector pumps, while two water-powered mills processed the extracted slate with six saws, three dressers, and three planers. Production figures show modest output of 350 tons with fifteen men in 1883, yet the quarry distinguished itself through specialized products including the ‘Parc’ patent ridging system, which generated substantial returns. Finished slate was transported via a short incline to a bridge crossing the Afon Croesor, then by further incline to junction with the Croesor Tramway at the Lower Parc incline.