Crystal refinery

This building refines the dragon crystals you harvest in the crystal craters. This means that the crystals you found are increased. The percentage of increasment is determened by the levels and number of crystal refineries in the town that harvests the crater. Per level a refinery increases the amount by 5 percent. The maximum is level 5 thus 25%.

Note:
To reach a level 5 refinery it wil cost you 210 crystals. Which means that you need to harvest at least 840 crystals with this city to start making a profit. This means that you need to harvest 8 craters with 150 crystals, up to 84 craters with 10 crystals.