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[Crystalr0se]

Has anyone ever heard of a terrestrial rock having multiple poles? Or a magnetic rock with no poles?

[Maxilos]

Hi,

Small physics lesson:

According to laws of physic multiple poles will nutralize eachother. Like a normal piece of iron, where all the poles are in different directions, it is not magnetic, unless you magnetize it. Even then it is not magnetic it only carries the laws of magnetism. when you remove it from the magnet, the poles turn to "chaos" and no magnetism! To make it magnetic you need to throw (for example a piece of non magnetic magnetite) in a immense strong magnetic field to correct the poles or let it struck by lightning (don't try this at home)!

A magnetic rock with no poles is not magnetic. The magnetic current always needs to run from one to another. Like electricity, if you have no poles (+ and -) there is no current (except superconductors). If you have one pole, still no current, it needs to run from + to - (theoretically - to +).

In my knowledge there are no terrestrial rocks having multiple poles or no pole, because physics, as I know it, doesn't allow it.

I hope I gave answer to your question.

Mark

[gemlover]

Mark is correct. in chemistry Hematite vs Magnetite is the difference between Fe2+ and Fe3+. Hematite (Fe2O3) is not magnetic (does not attract a magnet and can not be made to be magnetic) even though it is iron oxide. Hematite is 2 atoms of Fe3+ and 3 atoms of O2-. Magnetite (Fe3O4) is magnetic and can be made magnetic and it is also iron oxide. Magnetite is made with one atom of Fe2+ and 2 atoms of Fe3+ giving up 8 electrons to share with the 4 atoms of O2-.

Another thought came to mind with your original question, are you thinking about the determination of the magnetic poles of the earth by looking at the orientation of the magnetic minerals in a rock?

John

[Crystalr0se]

Very interesting, thank you Mark.

So is it possible for an extraterritorial rock to act this way?

[alfredo]

That's a good start, but the situation is more complex than that, because crystal structure plays a part in addition to the valence of the iron. The mineral maghemite, Fe2O3, just like hematite, with its iron in the 3+ state, is highly magnetic like magnetite! Crystal structure is different. I don't pretend to understand this - I'm just a dumb geologist and the physics is way over my head - but these minerals, like maghemite and others, exist and defy simple explanations about their magnetism.

[Crystalr0se]

No, I have a few rocks I found that when I put next to a compass and rotate it pushes and polls in several different locations suggesting that it has multiple polarity. A few of them that are from the exact same spot don't move the compass at all but still stick to a magnet. Iv never came across anything like this before.

Nicole

[Pete Richards]

If you really mean rocks, then it's possible that they contain several grains of magnetite or other magnetized minerals that have different orientations. Each mineral grain would only have one set of poles, but the different grains could (I think) have their poles oriented differently.

If you take loose magnets and bring them together, they align so that their poles are parallel. But if you were to mix up a bunch of magnets in an epoxy too stiff for the magnets to rotate freely, and let it harden, the overall mass would have very confused polarity while each magnet still had well-defined poles. The magnetic behavior at any given spot would be the sum of all the magnetic fields involved. It could be a mess....

I believe the magnetic behavior of magnetite is an intrinsic property of the structure, and not dependent on its crystalizing in a magnetic field. If so, different magnetite crystals, even growing next to each other, would have different pole directions, unless their axes were parallel.

[Josele]

Will not find a single crystal with many poles but is common in rocks due to unordered position of crystals, creating several magnetic fields interferences. I think these rocks could be hematite rich (antiferromagnetic, not produce magnetic field but is atracted to a magnet) and in some points rock could contain enough hematite to turn the compass.
You can find more information here:
https://www.foro-minerales.com/forum/viewtopic.php?p=77895#77895

Greetings.

[Maxilos]

I love good old physics (I'm studing it!) combined with my hobby! :)

Mark

[Pete Modreski]

That's very interesting, the photo of the hematite crystal lifting the magnet--I would not have realized it could do this! I presume that this must be one of those very strong, rare-earth magnets; I'm quite sure that an "old fashioned" iron bar magnet, would not be noticeably attracted to a hematite crystal.

[alfredo]

I can offer no physics explanations, but only the observation that the magnetism of hematite is highly variable, and a few specimens can be strikingly magnetic! Structural defects making some zones = maghemite"? Or exsolution lamellae of magnetite inside? I've no idea.

Another observation: the electrical conductivity of hematite is also highly variable. I've checked hematites from several localities with a metal detector; some react strongly, some weakly, some not at all. I neglected to check whether there is any correlation between magnetism and conductivity, so that's the next project....

[Josele]

Hematite is a antiferromagnetic material and are always attracted to a magnet, in greater or lesser degree, without need of magnetite inclusions.

Effectively, this neodymium magnet is very strong. One flat cylinder 6 x 3 mm weighing 0,65 g can lift easily a 500 g iron piece, more than 750 times his own weight!
In fact, with these magnets you can detect magnetism in almost all minerals containing Fe in his composition, even in some without Fe, as hubnerite!

Can see more pictures here:
https://www.foro-minerales.com/forum/viewtopic.php?p=77895#77895