Grey salt, also called Celtic sea salt or sel gris, is an unrefined sea salt hand-harvested from shallow evaporation ponds along the Brittany coast of France, its grey-blue color and slightly damp texture coming from the clay-lined ponds and retained trace minerals like magnesium and potassium. It differs from refined table salt, which strips out those minerals and moisture in processing.
Its flavor is mild and briny with earthy undertones, less harsh and more complex than table salt, which makes it popular as a finishing salt for meats, seafood, vegetables, and baked goods, and useful in dry brines given its natural moisture.
The harvest, carried out by workers called paludiers using techniques largely unchanged for centuries, remains an important part of Brittany's coastal economy and culture.