The Coal Mine is the main source of Coal [[File:icon coal.png|16px]], which can be sent for processing at a [[Toolworks]] to become Coal Tokens [[File:token coal.png|16px]] or it can be combined with Iron Ore [[File:icon iron ore.png|16px]] at a [[Foundry]] to create Iron [[File:icon iron.png|16px]] and Coal Tokens [[File:token coal.png|16px]]. In 4th era coal is being used as fuel in steelworks and from 5th era on it is needed as fuel in Coal Power Plant to generate electricity. Thus coal mining becomes critical throughout the whole game.

The base version of the Coal Mine generates 1 Coal [[File:icon coal.png|16px]] per [[Game tick]]. The capacity of the mine can be extended using 4 5 extension buildings that can be built on adjacent tiles to the base Coal Mine building. Three of the extensions provide a providing increase to the Coal [[File:icon coal.png|16px]] output of the minecould be build immediately, while the "Third Headframe" will become available in 5th era of the game. Of all extensions the "Second headframeand Third Headframes" provides provide the largest increase to Coal [[File:icon coal.png|16px]] production. The "Timber Tunnel Supports" extension adds a new process that consumes Timber [[File:icon timber.png|16px]] while providing a another large increase to Coal [[File:icon coal.png|16px]] production. When all extensions are built around a Coal Mine, it consumes 0.5 Timber [[File:icon timber.png|16px]] and produces 6 8 Coal [[File:icon coal.png|16px]] Per [[Game tick]].