Deep Navigation Colliery was a coal mine in South Wales, that operated from 1872 until 1991. Located next to the co-developed village of Treharris in the borough of Merthyr Tydfil, on development it was the deepest coalmine in South Wales Coalfield by some 200 yards (180 m). Producing the highest quality steam coal, it powered both the Cunard passenger steamers RMS Mauretania and RMS Lusitania in their successful attempts at the Blue Riband prize for the most rapid Atlantic Ocean passage. The mine is also thought to have been one of several locally that provided coal to the RMS Titanic; tests carried out on coal found in the ship's wreck have shown that most of the coal on board originated in South Wales. Amongst one of the first collieries in South Wales to have shafts wound by electricit