Series of shafts and spoil mounds dispersed across a large area, now interspersed with modern housing in Moel-y-crio. A large fenced-off shaft is located at SJ 1995 6970, while earthworks can be found surrounding Mount Villas at SJ 2020 6975.

Moel-y-crio Mine was located at the western end of the California Vein, which runs through Carboniferous Limestone. The mine was active for an extended period, with evidence of extensive workings spread throughout the area. In the early 20th century, from 1901 to 1906, the Central Halkyn Mining Company incorporated Moel-y-crio Mine into its operations. During this time, mining activity focused on working down shaft inclines (Smith, 1921).