Mines

The mines are your daily source of gemstones. These gemstones may be sold for 200 silver a piece. The Primary Mine is unlocked at level 15, with the left, middle, and right mines opening at level 30. The placement of these 4 mines determines how many of which gems an upgrade will require. If you do not have enough gems to upgrade a building, you may request friends send you gemstone.

Mine Upgrades
The Primary mine (picture featured being level 3) requires the following:

Lvl 1 - Free @ level 15 and produces 4 gems.

Lvl 2 - 38000 silver @ level 25 and produces 8 gems.

Lvl 3 - 62000 silver @ level 35 and produces 12 gems.

Lvl 4 - 90000 silver @ level 45 and produces 16 gems.

The Secondary mines (left and right pictured level 1 and middle pictured level 2) require the following:

Lvl 1 - Free @ level 30 and produces 4 gems.

Lvl 2 - 25000 silver @ level 40 and produces 6 gems.

Lvl 3 - 35000 silver @ level 50 and produces 8 gems.