What elements makeup the minerals feldspar, quartz and mica?
Clean it of what? Quartz is a good, resistant mineral, it will not dissolve in sea water, and brushing it with a cloth will not scratch it, because quartz is moderately hard (7 on Moh's scale). You could even etch it in dilute acid, which will remove any contaminants on the surface but not affect the quartz.
Quartz is strong enough to be used in watch crystals: it has a Mohs hardness of 7 if memory serves. Salt won't injure it in the slightest. Quartz won't heal anyone from a physical ailment, but they are pretty. Be well
soak them in raw apple cider vinegar. it should work
