Kala namak is a true rock salt, found in large large halitedeposits formed through evaporation of ancient seas and is mined from locations in the Pakistani Himalayas. It is then imported into India where it is converted to kala namak by heating to around 900C in the presence of natural reductive agents (usually either gum Arabic - Vachellia nilotica - or Salsola stocksii) until it melts, then it is cooled, stored and aged. The final kala namak consists mainly of sodium chloride, with trace impurities of sodium sulphate, iron sulphide and hydrogen sulphide. The sodium chloride gives kala namak its saltiness, the iron sulphide the purple-pink colour and the sulphur compounds the distinctive sulphurous aroma of a volcanic flavour.