Lleyn Peninsula Manganese Mines

Introduction
British manganese reserves are very limited. At times during the last century, particularly the Second World War, all of Britain's manganese came from North Wales. Small mines were worked in the Rhinogs and on the Lleyn peninsula as well as some outlying areas. Manganese was originally used as an oxidising agent for the manufacture of bleach. Following the discovery at the start of the 20th century that it could be used to harden steel it became a strategic metal.

Geology
The ore is present in several broken bodies in volcanic rocks.

Benallt & Rhiw Mines
Grid Reference: SH 221 281

Altitude: ~200m

Commenced 1858. During 2nd WW, Benallt was the largest operation. Ran by Ministry of Supply. 60,000 tonnes produced during WW2 cf. 195,000 tonnes during the lifetime of the mine. Number of levels at depths of between 60 and 180 ft accessed by shafts and winzes. Linked underground with Rhiw and Tyddyn Meirion Mine. Tramway lead down to a pier at Porth Iago.

Nant Mine
Grid Reference: SH 210 266

Altitude: ~100m

Further down towards the sea at Porth Iago. Large flooded underground stope with two entrances. Remains of machinery. Also large open stope and trial levels.

Llanaelhaearn
Grid Reference: SH 407 461

Altitude: ~350m

Dozens of small adits. Mostly collapsed. Three still accessible open in good condition but limited in extent. On side of Gurn Du. Spoil heaps shown on OS map.