the salts mined in the regions surrounding the Himalayas.
The raw material for producing Kala Namak was originally obtained from natural halite from mines in Northern India and Pakistan

Traditionally, the salt was transformed from its relatively colourless raw natural forms into the dark coloured commercially sold kala namak through a reductive chemical process that transforms some of the naturally occurring sodium sulfate of the raw salt into pungent hydrogen sulfide and sodium sulfide. This involves firing the raw salts in a kiln or furnace for 24 hours while sealed in a ceramic jar with charcoal along with small quantities of harad seeds, amla, bahera, babul bark, or natron.The fired salt melts, the chemical reaction occurs, and the salt is then cooled, stored, and aged prior to sale. Kala namak is prepared in this manner in northern India with production concentrated in Hisar district, Haryana. The salt crystals appear black and are usually ground to a fine powder that is purple.

Although the Kala Namak can be produced from natural salts with the required compounds, it is common to now manufacture it synthetically. This is done through combining ordinary sodium chloride admixed with smaller quantities of sodium sulfate, sodium bisulfate and ferric sulfate, which is then chemically reduced with charcoal in a furnace. Reportedly, it is also possible to create similar products through reductive heat treatment of sodium chloride, 5–10% of sodium carbonate, sodium sulfate, and some sugar.