Mining is a Technology Card which is gained automatically upon reaching the Expansion Period.

The Science Card (No. 35) requires 2 Coal, 3 Pick Axe, 1 Oak to unlock.

The card allows your Followers to start mining seams of Gold around the land if within their Abode's range which provides Gems for you to use as a God to buy Settlements and Resource Cards. Mining the land will slowly make the area where the gold was diseased and so the Beautify power has to be used to rectify this.