Black salt is also known as kala namak. It is a special type of Indian mineral salt with a distinctive / sulfurous flavor. Black salt or Kala Namak is not black, but more a reddish-gray, because of the presence of trace minerals and iron. It is not interchangeable with sea salt or table salt because of it's distinct flavor.
According to India's classical medical science, Ayurveda, black salt is full of therapeutic benefits. It is rich in iron, and is a cure for flatulence and heartburn.
According to Ayurveda doctors, black salt is the most beneficial form of salt because unlike ordinary salt, they don't increase the sodium content of blood and are therefore recommended for patients with high blood pressure and low-salt eating dieters. It is also a rejuvenator while aiding digestion and improving eyesight. It is said to aid in digestion and soften the bowel