Duranium
From Supremacy Wiki
Q: How do I get more Duranium?
A: Systems with Asteroids can build a structure that mines additional Duranium. Some empires have structures that mine extra Duranium (Cardassians, Dominion). There's also a universal structure that allows a lot more Duranium to be mined, but with a huge Morale penalty (Core Mining Complex).
