Foel Fawr Limestone Quarry or Herbert's Quarry is on the northern escarpment of Y Mynydd Du. It was in use during the twentieth century.

D.K. Leighton, RCAHMW, 1999.

Herbert's Quarry lies within the Fforest Fawr Geopark. The site preserves remains of lime kilns, quarries and spoil tips and date to the last two centuries. Herbert's Quarry is different to many lime producing areas in Wales where tramroads and canals provided the transport links, as it was served soley by Turnpike roads and other trackways.

In 2011/12 the Dyfed Archaeological Trust began a new project to investigate the lime industry of the Black Mountain entitled 'CALCH'. The Royal Commission engaged in a number of aerial surveys of the landscap during 2010-2012.

T. Driver, RCAHMW