There are numerous seams of which the Main Coal is the principal one, being some 3 to 4m thick.
[2] The full sequence is: Mining was taking place before the 16th century, largely in connection with a local sea-salt industry.
Similar but very small scale activity also took place on the northeast coast of the nearby Isle of Arran.
It continued at a low level through to the late 18th century when a new pit was sunk at the Argyll Colliery, ushering in the coalfield's busiest period which lasted until the closure of the mine in 1929, following a fire in 1925.
In 2010 Campbeltown born artist, Jan Nimmo, completed a documentary film, "The Road to Drumleman: Memories of the Argyll Colliery", which tells the story of Kintyre's last mine, the Argyll Colliery, through the narrative of some of the remaining miners.