Sel Gris is Fleur de Sel that has been allowed to settle and is raked from the bottom of the pond where it gathers some minerals causing the gray color. This salt is mineral rich, solar evaporated and sun-dried to a moisture content of 8% to 13%. That moisture content is an important feature and has a practical application in cooking and you can rehydrate your salt if needed.
This is really the single essential salt and all you would need to cook well. Use in most any cooking application and for finishing hearty or very moist foods. Perfect on a steak, chops, or hearty vegetables.