OK, it’s time to get real.
I’ve eaten my morning breakfast cereal, Total, at my desk. I walk over to a lab at Los Alamos, and stumble into the field of a 100 Tesla blast(the Los Alamos record is repeatable, BTW).
Then what, vis. a vis. those ferric/ferrous materials? (I’m dying to have the answer be yes, with iron particles spraying out, like some kind of superhero–MagnetoMan!)
I don’t think anything would happen because the particles are too small and won’t be pulled much by the magnetic field (you are only talking about milligrams; even 100% of the RDA for iron is only 18 mg), plus they will dissolve pretty quickly and be dispersed by chewing/stomach action (I don’t know exactly how fast, but one could test it with a 1-2 pH HCl solution and iron particles extracted from cereal; of course, it takes some time for your stomach to acidify its contents).
I think you can get some idea by looking at tattoos. The ink presumably contains more iron oxide than you get from a bowl of cereal. Generally there is no reaction, sometimes there’s burning, but no iron, ah, being liberated from your body.
To expand on this, many (most?) metals form compounds in different oxidation states, that is, they lose different numbers of electrons and so can combine with different numbers of ions to form salts. So iron can be Fe[sup]2+[/sup], which can combine with, say, two Cl[sup]–[/sup] ions to form FeCl[sub]2[/sub], or Fe[sup]3+[/sup], which can combine with three to form FeCl[sub]3[/sub].
The traditional naming system takes the root name of the metal, in this case “ferr”, from the Latin name used in the element symbol Fe, and adds -ous or -ic, depending on the oxidation state. Similarly, you can have cuprous or cupric salts (copper), stannous or stannic (tin), titanous or titanic (titanium), and so on. “-ic” signifies the higher oxidation state.
This is of course separate from the everyday use of the term “ferrous metal”.
I genuinely didn’t know that powdered metallic iron was put into cereals. Sounds like a cheap trick to me. I think I’d prefer to get my iron from an occasional steak.
As for the ferrous iron – Iron also has an austenitic phase at higher temperatures. This phase is non magnetic. Addition of certain alloy metals can bring the transition temperature down below room temperature. So yes: there is such a thing as non-ferrous iron.
A reactive metal like iron is not going to stay metallic very long in the human body. It is probably oxidized before leaving the stomach even.
Also, many wannabe druggies or car tuners became very disappointed when they purchased nitric oxide.