I've always heard that snake mites are black. As far as remedies Provent a mite or a generic Permethrin lice/mite solution should work. Make sure they're snake mites and not some other pest.
I was possibly thinking wood mites but I've also heard that snake mites are not black while in a certain stage of development. I ordered a can of prevent a mite so I will be treating them with that. I have photos of the mites but am not sure how to post them.