The so called refined salts what is the procedure of refinement?

The salt companies invaribaly powder the crystal salt and add some free flowing agents. What knid of purification is possible in dry form. No company is dissolving the salt to separate dissolved impurities, If the salt companies make salt from sea water we can be sure they are purifying it. It is also not done. All their tall claims are hoax ? They earn huge profit just by powdering farmers salt and sellling at a premium price at the same time cheating common man?