Mining in Wales provided a significant source of income to the economy of Wales throughout the nineteenth century and early twentieth century. It was key to the Industrial Revolution.
Wales was famous for its coal mining, in the Rhondda Valley, the South Wales Valleys and throughout the South Wales coalfield and by 1913 Barry had become the largest coal exporting port in the world, with Cardiff as second, as coal was transported down by rail. Northeast Wales also had its own coalfield and Tower Colliery near Hirwaun is regarded by many as the oldest open coal mine and one of the largest in the world. Wales has also had a significant history of mining for slate, gold and various metal ores.
There had been small-scale mining in Wales in the pre-Roman British Iron Age, but it would be undertaken on an industrial scale under the Romans, who completed their conquest of Wales in AD 78. Substantial quantities of gold, copper, and lead were extracted, along with lesser amounts of zinc and silver. Mining would continue until the process was no longer practical or profitable, at which time the mine would be abandoned. The extensive excavations of the Roman operations at Dolaucothi provide a picture of the high level of Roman technology and the expertise of Roman engineering in the ancient era.
There is evidence of mining in the Blaenavon area going back to the 14th century, and there is evidence of mine workings at Mostyn as far back as 1261, but it is believed to have been practised even as early as Roman times. The coal mining industry burgeoned throughout the Industrial Revolution and into the 19th century, when shafts were sunk to complement the open-cast mining and drift mining already exploiting the ample and obvious coal resources.
During the first half of the nineteenth century mining was often at the centre of working-class discontent in Wales, and a number of uprisings such as the Merthyr Rising in 1831 against employers were a characteristic of the Industrial Revolution in Wales, Dic Penderyn became a martyr to industrial workers. The Chartist movement and the 1839 Newport Rising showed the growing concerns and awareness of the work force of their value to the nation. Although the Factory Acts of the 1830s and resultant Mines Act of 1842 were meant to prevent women and boys under 10 years of age from working underground, it is believed they were widely ignored. To replace female and child labour the pit pony was more widely introduced. Much later, in the middle of the 20th century, mining was still a hazardous enterprise, resulting in many accidents and long term ill-health with many retired miners still suffering from silicosis and other mining related diseases.
Incorporating the existing Coity colliery and Kearsley's pit (sunk in 1860), the Big Pit opened in 1880, so called because it was the first shaft in Wales large enough to allow two tramways. At the height of coal production, there were over 160 drift mines and over 30 shafts working the nine seams in the Blaenavon locality. Big Pit alone employed some 1,300 men digging a quarter of a million tons of coal a year. Large amounts of coal were needed to supply the local ironworks, as it took 3 tons of coal to produce a ton of iron. Blaenavon 'steam' coal was of high quality and it was exported globally. Burning hotly while leaving minimum ash, it was ideal to power the steam engines that drove steamships, Dreadnoughts of the Royal Navy and steam locomotive railways across the world.
However both economics and politics after World War I with its resultant general strike, the 1930s Depression and later Nationalisation and the miners' strike of 1984-1985 took their toll and all the smaller pits were either abandoned or swallowed into Big Pit's encroaching search for new seams. Finally in February 1980 the coal ran out and even Big Pit, then the oldest mine in Wales, had to close.
There are still nine headstocks remaining in Wales, including Big Pit (the metal frame erected in 1921 during the Miners' Strike of that year, to replace a wooden structure).
There is a well-known mining song part in Welsh and part in English.
I am a little collier and gweithio underground
The raff will never torri when I go up and down
It's bara when I'm hungry
And cwrw when I'm dry
It's gwely when I'm tired
And nefoedd when I die
The complete English translation is the following.
I am a little collier and working underground
The rope will never break when I go up and down
It's bread when I'm hungry
And beer when I'm dry
It's bed when I'm tired
And heaven when I die
Big Pit museum at Blaenavon
The Big Pit National Coal Museum is located at Blaenavon, and in 2005 it won the prestigious Gulbenkian Prize for museum of the year. It is one of only two remaining mines where it is possible for visitors to journey to the underground workings some 300 ft (90 m) below using the same cages that transported the miners.
Other museums preserving the memories and heritage of the coal mining industry in Wales are at :
South Wales Miners' Museum near Cymmer
Cefn Coed Colliery Museum near Crynant
Rhondda Heritage Park near Trehafod
Following the miners' strike, the only two deep mines remained working in Wales. Tower Colliery, Hirwaun, had been run by a miner's co-operative since 1994. Due to dwindling coal seams, the colliery was last worked on January 18, 2008 and the official closure of the colliery occurred on January 25. Mining continues at Aberpergwm Colliery, a smaller mine closed by the National Coal Board in 1985 but reopened in 1996. Several other small mines still exist, including the Blaentillery drift mine near to the Big Pit National Coal Museum.
List of mines in Wales
Aberpergwm (anthracite coal, drift mine, active in 2014 with 64 employees 
Bedwas Navigation Colliery (closed 1985)
Bersham Colliery (closed 1986)
Big Pit National Coal Museum
Blaenant Colliery (closed 1990)
Cefn Coed Colliery Museum
Celynen South Colliery in Abercarn (closed 1985)
Cynheidre Colliery (closed 1989)
Deep Navigation Colliery, Treharris (Closed 1991)
Ffos-y-fran Land Reclamation Scheme (Still under consideration as of 2013)
Gresford Colliery (closed 1973)
Lady Windsor Colliery in Ynysybwl (closed 1988); linked underground to Abercynon Colliery (Closed 1988)
Mardy Colliery in Maerdy (closed 1990, site cleared and now occupied by Avon Rubber); linked underground to Tower Colliery
Mostyn Colliery (closed 1887 after flooding)
Nantgarw Colliery (amalgamated with Windsor Colliery in 1974, closed 1986); deepest pit in the South Wales Coalfield when sunk in 1915
Nine Mile Point Colliery at Cwmfelinfach (closed 1964)
Oakdale Colliery at Ty Mellyn in the Sirhowy Valley (closed 1989; linked to Markham and Celynen North)
Prince of Wales colliery in Abercarn closed 1959. Greatest mining disaster in Gwent, 1878.
Point of Ayr (closed 1996)
Universal Colliery at Senghenydd, site of the Senghenydd Colliery Disaster; converted to a ventilation facility for Windsor Colliery and then closed in 1988
Seven Sisters anthracite; closed 1963
Tower Colliery (closed 1994 and re-opened after an employees' buy-out by Goitre Tower Anthracite in 1995; closed 2008 after exhaustion of the seam, but with plans to build an open-cast mine in its place)
Windsor Colliery in Abertridwr, Caerphilly; closed 1986
Wyllie Colliery in the Sirhowy Valley; closed 1968
Bryntail lead mine (No longer in use)
Cilcain lead mine (No longer in use)
Clogau Gold Mine
Dolaucothi Gold Mines
Great Orme copper
Gwydir Forest various metal mines
Gwynfynydd gold mine (No longer in use)
Klondyke mine lead mine (No longer in use)
Llywernog Silver Lead Mine
Minera Leadmines (No longer in use)
Parys Mountain copper mine
Sygun Copper Mine (no longe in use as a mine)
Van Leadmine Llanidloes
Jones, Barri; Mattingly, David (1990), "The Economy", An Atlas of Roman Britain, Cambridge: Blackwell Publishers (published 2007), pp. 175–195, ISBN 978-1-84217-067-0
The History of the Parishes of Whiteford and Holywell; Thomas Pennant, 1796, p.133
"Coal mine closes with celebration". BBC News. January 25, 2008. Retrieved 2008-01-25.