What would natural mineral salt be good for?
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If you mean a salt that is sold for food use, in one sense it's just salt. Use it tobring out flavor in foods as you would any other salt -- table salt, sea salt, kosher salt -- they are all basically sodium chloride. Some salt has been purified, sometimes with anti-caking minerals added; that's what we call table salt. Salt can be extracted from sea water or from earth sources (often mined), and when it's in its natural state it has more minerals which may make it pink, gray, black.... Kosher salt has a different crystalline structure and has no added chemicals.
Sometimes the natural salts have distinctive tastes, and are used at the end of cooking, sprinkled on the food, called finishing salts.
Some salts taste 'saltier' than others, so you have to check so you don't oversalt.