It is repeated often that Saharan calimas are fertilizing often Atlantic ocean. But I suppose that most of Saharan dust contains Fe2O3 and not FeO. Am I right?
I think you are correct. Typical sand is silica (white) with a little Fe2O3 (red) to give a "sand" color. FeO is black and over geological time in air, oxidizes further to Fe3O4 with hydroxides and hydrates (black and dark brown) and eventually Fe2O3.