Russia - Civilian Buildings
 

Gold Mine, Coal Mine, Iron Mine

To begin extracting coal, iron or gold, build a mine on the deposit. Then assign peasants to the mine so they start the extraction. To increase the limit of workers a mine can hold, carry out series of mine infrastructure upgrades. The final 7th mine upgrade allows 95 peasants to work in a single mine.

You should defend your mines, because an enemy can capture them.