The Cambergi Slate Company Limited was formed in 1873 to work the quarry, with a 10,000 £20 shares offered to the public.

They proposed that a branch of the Corris Railway was built along Cwm Hengae to the Cambergi mill, but construction of this did not begin.

However, the slate was poor quality, and in 1877 he began work on Hengae quarry on the opposite side of the valley.

[1] In 1889, the quarry lent its mill to house the local Eistedfodd,[6] but Griffiths continued to struggle financially.

[1] The main quarry site was an open pit high near the summit of Mynydd Cambergi, about 800 feet (240 m) above the floor of the valley.

[1] At the foot of the incline, on the south side of the road, was a slate-built mill, containing nine saw tables and a slate planer.