Rock salt or sendha namak, as it is popularly known, is a favorite of those fasting. Rock salt is the purest form of salt - unprocessed and raw, devoid of environmental pollutants and chemical components. "It contains 84 out of the 92 trace elements required by the body including potassium, iron, calcium, zinc, magnesium, copper and so on. It's a superior salt, according to Ayurveda.