Mining

 is one of the developable Technology Branches in The Colonists.

Levels
Without any research, you only have a level 1 Surface Mine which can mine Stone. At mining level 1 you can now mine clay, iron, and coal with your newly unlocked level 2 surface mine and shaft mine. At mining level 2 you can mine salt, gold, and quartz with your newly unlocked level 3 surface mine and level 2 shaft mine.