Craig Rhiwarth quarries are located above, and to the immediate north of, Llangynog in Cwm Pennant. They are hillside quarries with some underground workings. A quarry here was in existance by 1705, and possibly as early as the sixteenth century. In early workings, material was sledged down to the valley floor some 800 feet (244m) below. The quarry was very active in the first decade of the nineteenth century when an incline was installed. This was replaced by another incline to the west during mid-nineteenth century development when further galleries were opened up and an extensive two-foot gauge tramway sytem laid down. Later working was underground. Material was carted, possibly for river carriage, later to the canal at Llanymynech, and after 1871 to the railhead at Porth-y-waen. Output in 1856 was 1000 tons. In 1882 329 tons was produced by 15 men.
After declining during the later nineteenth century there was some temporary revival when the Tanat Valley Railway opened and the incline extended under the road to exchange sidings at the terminus. In the 1930s there was some limited activity when men moved here after the closure of West Llangynog quarry, with 26 men employed in 1937-8, but final closure came in 1940-1.
The quarry is believed to have shared facilities with both the adjacent lead mine (NPRN 34007) & roadstone quarry (40614).
Surface remains (in 1991) include the inclines with associated structures, various ruined building (including a magazine), in addition to the surface workings. Underground workings were still accessible in the mid-1980s.

Sources:
Ordnance Survey County series 25-inch maps: sheet Montgomery IV.12, editions of 1887 & 1901.
RCAHMW air photos: AP955008/62-4
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), 199-200.
Williams 1985, The Old Mines of the Llangynog District, pp.117-8 & fig.26.
RCAHMW AP955008/62-4

David Leighton & J.Wiles, RCAHMW, 26 January 2015