What is the best mineral foundation for covering dark spots caused by acne?

I've tried concealer which didn't work,I've tried liquid foundation which didn't work,And i've tried exfoliating.So i'm left with trying a mineral foundation.I wanna know which one is the best but also not to expensive max i'll pay for makeup is $15.What is the best mineral foundation for covering dark spots caused by acne?
bare escentuals. that's the BEST, there are other products, but, I've used this for years with many compliments...

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