Sel de Guerande is hand-harvested on the Celtic sea coast in Brittany. It is a nationally preserved area and registered as a World Heritage Site since 2002. The salt is obtained by sun and wind evaporation and it is neither filtered nor cleaned thus it is free of pollutants from mechanical and chemical processes. This salt is composed of only 71 to 74% of sodium chloride (for comparison most of the others salts are 98% sodium chloride), (ref: Dr Brian Clement). The remaining percentage is composed of bio-available minerals and trace elements (calcium, potassium, magnesium, iron, manganese, sulphur, zinc, iodine and other nutritive elements).This is why it is grey.