Ruby

Rubies are the most important currency for your growth. Districts 3 to 10 cost mostly rubies, as do the stadium and the pig iron mine's upgrade to level 3.

Where from

• Pig iron mine: very rare, the more it produces, the sooner
• Mesas: many small mesas carry a visible red crystal. Demolish them and the rubies are yours (Boulders, Mesas and Toxic Lakes)
• Tutorial: one guaranteed ruby, plus one in the gifted kryptonite mine
• Login bonus: on the last day of the calendar
• Shop: one at a time for 250 Urplasma

What for

• districts from the third on (District Prices)
• the stadium
• pig iron mine level 3