All of the land designated as Phoenix United Mine SSSI is owned by the Duchy of Cornwall.

[2][3] The 29.8-hectare (74-acre) SSSI, notified in 1996, is located within the civil parish of Linkinhorne, on the south-eastern edge of Bodmin Moor, 5 miles (8.0 km) north of the town of Liskeard.

[4][5] The SSSI also forms part of Phoenix United Mine and Crow's Nest Special Area of Conservation.

This has restricted the growth of vascular plants and has allowed bryophytes (mosses and liverworts) and lichens to flourish.

The mine is one of only two sites in the world where Cornish path moss (Ditrichum cornubicum) grows, the other being Crow's Nest.