Kala-Namak Salt is a salt often used in indian cuisine, especially for meals which are supposed to smell and taste egg-like without containing egg. For example, you can prepare very nice scrambled tofu.
In order to produce Kala-Namak Salt the fruits of the tree terminalia chebula are boiled dry with salt. Thus, the salt obtains colour and taste of these fruits. The high proportion of hydrogen sulfide and iron they contain is responsible for the egg-like taste and smell.
Please store in a dry place.