Operations Aberllefenni Slate Quarry

map of aberllefenni area quarries , tramways

one of reasons aberllefenni slate quarry s continued use high quality of slate extracted. there 2 major bands of slate running parallel each other through region of mid-wales, broad vein , narrow vein , latter of aberllefenni extracted. broad vein of considerably poorer quality narrow vein, , slate produces of little use in roofing slates or polished surfaces. instead used in walls, fences , hardcore. narrow vein of better quality , used in higher quality applications , fetched higher prices.

slate extracted narrow vein @ aberllefenni deep blue , extremely hard , dense. resists fine splitting, of mines product large cut slabs rather split roofing slates. foel grochan mine consists of 8 near-horizontal tunnels @ approximately 60 feet (18.3 m) vertical separation. these bored valley side north of near-vertical narrow vein. each tunnel connected large chamber rock extracted. these chambers ranged 100 187 feet (30.5 57.0 m) in length 24 30 feet (7.3 9.1 m) of rock left between bottom of 1 chamber , top of next lower chamber. more slate extracted, several of upper chambers joined vertically form extremely large cavern known twll golau open @ top.