Kala Namak salt also known as black salt or bire noon is a type of rock salt and is mostly found in the Himalayas. This salt adds an egg flavour to savoury dishes and is popular with vegans. It contains greigite (Fe3S4, Iron(II,III) sulfide) and as a result, forms brownish pink to dark violet translucent crystals when whole. When ground, it’s colour ranges from purple to pink.
Kala namak has been praised in Ayurveda and used for its perceived medical qualities.