A small magazine marked on the 1901 OS map, probably associated with Fochriw Colliery. Of rubble stone walls bonded in ash and lime mortar with yellow brick quoins and dressings, it measures 5.4m E-W x 4.2m. It originally had a monopitch slab roof, a small section of which is still in situ. Inside is a collapsed brick vault, clearly visible at springing point. The S wall is the highest, surviving up to 2.4m, the N wall to 1.9m, whilst the other walls are lower. On the W side, the entrance is protected by an L-shaped wall, now at a low level.
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H & H, 16/09/2013.