How should I store the salt and does it have a shelf life?

Like any unrefined rock salt, this product has no true expiry date — salt is a mineral and doesn't support microbial growth. However, the coarse crystals are hygroscopic: they absorb ambient moisture, which leads to clumping and, over time, a slight dulling of the volatile sulphur aroma that defines kala namak. Transfer the salt from the original pouch into a glass jar with a tight-fitting lid (or a ceramic salt pig with a lid) and keep it in a cupboard away from the stove, dishwasher, or windowsill. If clumps form, they're harmless — break them up with a spoon or give the jar a shake. Avoid storing it in a metal grinder long-term; the sulphur compounds can react with certain metals, imparting off-flavours. A ceramic or acrylic mill is ideal for daily use, with the bulk reserve kept sealed in glass.