Three terrace working with incline and powder house. The formation of the incline that once carried slate down to the mill remains visible across the hillside. Additionally, evidence of a trial working can be found to the northwest of the main quarry site.

Plas y Nant was a three-gallery hillside quarry that opened in the mid-19th century. By 1883, a workforce of 28 men was producing 672 tons of slate annually. The quarry’s output was transported down an incline to a small processing mill below. Although the North Wales Narrow Gauge Railway ran nearby, the quarry never had a direct rail connection to the line. After a period of dormancy, some limited working took place at the site following the Second World War.