Also spelled fiore di sale.
Hand-harvest and untreated, the 'flower of salt' is moister and has larger crystals than typical table salt, and is rich in potassium and magnesium. And it's much pricer as well.
In Italy, much of it comes from the historic salt pans by Trapani. In trendy Italian restaurants, you'll often see the French version, fiore di sale di Camargue (France).
Image by Algor7, Creative Commons License