This salt  contains  less sodium chloride than
commercial sea salt (86% sodium chloride vs. 99.99%).

Thank you rachel for this information about salt . I knew that refining was
bad but didn't know to what extent .
Are you sure about 86 % ? i thought he will be more than that. Would you
have the exact composition of 14 % left.
If the brand name celtic salt comes from "les marais de guerande" in the
south of britanny ( France) i know the place . It is salt marches that have
been digged out and dikes were built to make lot of different basins . The
tides fill the basins and after closing the dikes are left to dry . Then the
salt is scrapped with long wooden rakes.
That way the salt is mixed with little bit of everything that is in thoses
muddy flat. That explain the high mineral content other than sodium
chloride, and the gray color.
In france i was using this one but when i moved here ,before i found celtic
salt i used rock salt from Utah ( unrefined mined salt from old marine
deposit ) it have little bit of a red dots in it  that is the red clay of
utah. Celtic salt is way tastier and before i found it i was prefering to
drink sea water to fulfill my special  sodium needs .
jean-claude