Fleur de Sel (flower of salt) has calcium, magnesium, potassium, and contains varying quantities of iron, zinc, manganese, and literally dozens of other trace minerals.
These combine with the sodium chloride that makes up the majority of the salt to achieve an extremely well-rounded, mellow finishing salt.
Fleur de sel is produced by collecting the thin layer of salt that rises to the surface of shallow pools of seawater.
Because of its delicate nature and higher price relative to other salts, fleur de sel isn’t meant for seasoning a dish while you cook it. If you expose it to high temperatures, it will melt and lose its unique character.
Instead, you should use sprinkles of fleur de sel on anything that needs a little extra oomph right before it’s consumed: salads, fish, meat, fruit, vegetables, and dessert. Some even sprinkle it on their oatmeal.