There are five ratings of a planet's mineral richness. This affects a planet's production capacity as well as the population growth of lithovore races. If we use Abundant rating as the baseline, an Ultra-Poor world has a production rate of only 62.5%, while an Ultra-Rich world has a production rate of 206.25%.
The probability for each richness category depends on the system's star: the hotter and younger the star, the richer its planets are likely to be. For instance, a planet orbiting a blue-white star will always be Abundant at the worst: they have 0% chance of being Poor or Ultra-Poor. On the other hand, a planet orbiting a red star has 0% chance of being Ultra-Rich and only 1% chance of being Rich. In general, Abundant planets are the most common, with a percent chance between 30% and 46% depending on star class. Blue-white and white stars are more likely to have Rich planets, while orange stars are more likely to have poor planets.
Regardless of star type, the homeworlds of major civilizations are normally Abundant unless changed to Poor, Rich, or Ultra-Rich with a racial trait; by default, this only concern the Bulrathi who start with a Rich homeworld. Random events can also increase or decrease a colony's mineral richness.