Fron Boeth Quarry
Fron Boeth Quarry was opened in 1886 as an extension of the Pant Mawr quarry. It was never very successful and was closed in the early 1900s. The quarry is situated to the east of Cwm Croesor and the quarry's products were shipped out via the Croesor Tramway via a short incline to a 500 yard long tunnel through the mountain to access the top of the Pant Mawr incline. 
A Cornish boiler still survives in the quarry.
- Richards, Alun John. The Slate Regions of North and Mid Wales and Their Railways. Wales: Carreg Gwalch. ISBN 0863815529. OCLC 59415611.