Four run in adits.*

The easternmost adit retains a tiny shelter. The third adit contains the most notable feature: a keyhole powder house with an eight-foot diameter circular subsurface chamber and a roof formed from inclined slate slabs, accessed via a ten-foot long, eighteen-inch wide slab-covered passage. Such powder houses were known in the Ffestiniog area, though they were much larger, and only one intact survivor is known at Graig Ddu. The second adit has a partly underground shelter. The westernmost adit shows fragments of a tiny structure, likely related to the short-lived trial work.

A series of exploratory investigations were carried out in the mid-1870s during a period of optimism for the Beddgelert slate field. The work ultimately failed to meet expectations, with insufficient quality or quantity to justify full development. Trimming waste indicates some good-quality rock, though not enough to sustain a viable quarrying operation.