For the sake of salt, Rome created a system of remuneration (from which we get the word "salary"), nomads domesticated the camel, the Low Countries revolted against their Spanish oppressors, and Gandhi marched against the tyranny of the British. Through the ages, salt has conferred status, preserved foods, and mingled in the blood, sweat, and tears of humanity. Today, chefs of haute cuisine covet it in its most exotic forms--underground salt deposits,...