Halite, Rock salt.

Halite, Rock salt.

Halite, or rock salt is sodium chloride (NaCl).This is an evaporite mineral which has precipitated from evaporating sea water. The "dirty" colour is due to contamination by impurities. This specimen from a Cheshire salt mine requires extra care in storage due to it's tendency to decompose in humid conditions, and become very wet. This specimen is stored in an airtight box,with a good number of dessicant sachets, but even so is still liable to become slightly wet.