We get this question quite often, and the answer may surprise you. Mineral makeup is not organic but 'inorganic'. Being of mineral origin, it is inert, and doesn't breakdown the way, say, flower petals do. Because it's inert, mineral makeup don't require preservatives to stay fresh, and it has great longevity.
How do some mineral cosmetics manage to call themselves organic? They add a little organic something - corn starch, lavender oil, or plant extracts, for example. Just a little bit, and they can claim to be 'organic minerals', however non-sensical that may sound to a chemist. And with that they need preservatives, because they are no longer inert.
We prefer to keep it simple. Pure minerals, and nothing more. It's really all you need.