[2] It was located at Corris Uchaf about 5 miles (8.0 km) north of Machynlleth, in Gwynedd, north-west Wales.

[1] In 1869, a lease was granted for the property and there is an 1871 report by John Imray on the quarry which describes a well-developed concern, although it was not then connected to the Upper Corris Tramway.

By March 1877, all the equipment for the new quarry was installed and a large number of men were being hired to work there.

In 1899 it was closed for a month while a new steam engine was installed,[6] and 200 men are recorded at work at the turn of the century.

Some quarrying took place in 1924, producing slabs for "cisterns, billiard tables and electrical switchboards", though details of the ownership were still in dispute.

[2] The Abercwmeiddaw mudstone beds underlie the Rhiwlas Formation that runs through mid-Wales to Bala.

In some locations these mudstones are highly cleaved, forming a vein of slate that is suitable for commercial quarrying.

The first workings here were underground, and the binocular tunnels were driven into the hillside to reach the Broad Vein.

A short water-balance incline was used to lift blocks of slab up from this lower tramway to the mill level.

High retaining walls were built on the north bank of the Afon Deri to hold back the waste tips on the narrow site.

The 1906 advertisement listed a "Locomotive engine with vertical multitubular boiler, 2 6in cylinders, four wheels coupled 2ft 3in gauge by H & J Ellis".

It is likely the locomotive was a standard De Winton product[7] that had been resold by Salford engineering company H & J Ellis.

Though circular saws were common in the Welsh slate industry, the Hunter variants were the first to have replaceable tips.

Hunter patented his circular saw in 1855, and licensed their production to companies including De Winton.