Kala namak, also known as Himalayan black salt, is an interesting savoury salt containing sulphur compounds which contributes to its unique umami flavour and pungent smell (like hard boiled eggs).
Kala namak is key to giving an "egg-y" flavour to dishes such as vegan omelettes, quiches, frittatas, egg salad, and tofu scrambles. Also common in Indian cuisine. As the sulphuric flavour dissipates when cooked, use as a finishing salt.
Although the salt appears black in rock form, it changes to a light pink colour when ground.