Maenofferen (also known by its variant spellings Maen-Offeren, Maen Y Fferem and Maen Offeren) Slate Mine forms part of the extensive Blaenau Ffestiniog complex of mines that occupy the area between the Manod and Moelwyn Mountains. Maenofferen is one of the higher level mines, with the processing floor at over 400m above sea level. It began operating on a piecemeal basis in the late 18th Century, principally as part of an open cast mining area, known as David Jones’ pit. The first company to formally extract slate was the Maenofferen Slate Quarry Company Ltd formed in 1861, when the land and existing quarry was leased from the owner Lord Newborough. The quarry proved very successful, its output increased from 397 tons in 1861 to 8,600 tons in 1882, the fifth largest producer in the Ffestiniog area. In 1897 it employed 429 people, but by 1972 this had fallen to 60 men with an annual output of 1,200 tons. Quarrying still continues on the site today - with Maenofferen now owned by J. W. Greaves and Sons Ltd, Blaenau Ffestiniog - although underground operations ceased in 1999 and none of the above ground complex of buildings at Maenofferen remains in use.
The below ground mine workings of Maenofferen Slate Mine occupy an area approximately 1922m by 480m by 225m and the associated above ground complex of buildings and infrastructure are indicative of many phases in the quarries development. The quarry therefore provides considerable information for understanding the development and process of underground extraction, the above ground processing, and the onward transport of the slate, to its worldwide markets.
A detailed survey and investigation of the mine was carried out by the Royal Commission in 2010.
Lindsay, J. 1974 History of the North Wales Slate Industry, David and Charles, London
Gwyn, D. 2006 Gwynedd: Inheriting a Revolution - The Archaeology of Industrialisation in North-West Wales, Phillimore, Chichester
Louise Barker & Spencer Gavin Smith, RCAHMW, August 2011