FMF - Friends of Minerals Forum, discussion and message board

[jonas winslo]

Magnetite is an oxide of iron (as is hematite). It is not a component of ordinary rust, although it can form as iron oxidizes in a dry environment. When you see sparks from welding operations or from iron striking a hard surface (as when it is held against a spinning grinder), the sparks are due to the rapid (and exothermic) oxidation of tiny particles of iron into magnetite.

Magnetite is a natural magnet, hence the name, giving it a very nice distinguishing characteristic. Explaining the magnetism is not easy but here is a go at it. Remember, electricity produces magnetic fields just as magnetism produces electric fields. Magnetite is a member of the spinel group which has the standard formula A(B)2O4. The A and B represent usually different metal ions that occupy specific sites in the crystal structure. In the case of magnetite, Fe3O4, the A metal is Fe +2 and the B metal is Fe +3; two different metal ions in two specific sites. This arrangement causes a transfer of electrons between the different irons in a structured path or vector. This electric vector generates the magnetic field.

[Jordi Fabre]

Hi Jonas, welcome to FMF

I separated your post of the thread Magnetite as pseudomorphs of Garnet? Blue River Skarn, Russia where you posted it originally because your answer is not directly related with the question posted for George Balogh.

Anyway, very good text and very interesting topic, I assume that some others FMFers will follow your footsteps... ;-)

[Don Lum]

Hi Jonas,

Welcome to The Forum.

It has been a long time since my first chemistry and physics courses (1963-4) and I am certain a lot has been learned since then but I have a question.

Is the direction of the spin in the outer shell of the electron orbit a determinant of whether a substance is magnetic or exhibit magnetic properties?

Thanks.

Don

[Roger Warin]

Hi,
Magnetite is a double oxide of iron II and III. It has a spinel structure, as Jonas pointed. It is a refractory mineral typical of igneous rocks (also meteoritic ones) in which it is disseminated. It is often associated with ilmenite.

So I see magnetite disseminated in feldspar or metamorphic rocks, but not in substitution of another mineral, yet it was a garnet.
Magnetite is formed at high temperatures in a liquid magma. It is concentrated by gravity on the floor of magma chambers. Magnetite may also form in metamorphic rocks at high temperatures.
After erosion, magnetite occurs in heavy sands from detrital sedimentary rocks.
It is not uncommon in residues of gold panning.
It is often confused with micrometeorites, but then it is an artifact due to the magnetic properties.
Roger.