Salt is one of the most valuable minerals on the planet. Wars have been fought over it. It is essential to producing good flavors in food - as it assists our tongue and saliva in communicating the food signals to the brain. It was even more important in the times before refrigeration was widespread as a preservative for food (think Jerky).
I have a wide collection of salts - these two in particular are from Hawaii - one covered in red mineral clay which imparts a somewhat bitter finish to the salt, and the other with volcanic charcoal which acts a bit as a palette cleanser.