Boulder purity

I know that purity of boulders depend on mining set, distance from the ladder and the debth of the mine.
My question is if M&M of the miner is used in equation ?
And if it is does it have a soft cap (diminishing returns) after certain number of M&M profficiency?
My question is if M&M of the miner is used in equation ?
And if it is does it have a soft cap (diminishing returns) after certain number of M&M profficiency?