I've been considering filling my alien world with a plethora of magnetic creatures, all of which use magnetism in unique and creative ways. Of course these creatures are only going to be one genus, but still I'd be interesting to see. These creatures have hard metal coatings like scaly-foot gastropods, critters that are mentioned in every single metal creature question on this site. These ferrous exoskeletons initially serve as defence against predation but allows some creatures to exploit magnetism. At some point I came up with the idea of an alien coating itself in magnetite sand (ironsand) and using it as a first line of defence, the exoskeleton being the second.

It is typically dark grey or blackish in colour. It is composed mainly of magnetite, Fe3O4, and also contains small amounts of titanium, silica, manganese, calcium and vanadium. Ironsand has a tendency to heat up in direct sunlight, causing temperatures high enough to cause minor burns.

Slightly burning the mouth of predators is fun and all but if faced against an armed human, like poachers for example, how good would this defence be? Sand being hard to compact makes for a very good shock absorber. As proof of this sandbags are often used in military context.

The theory suggests that about 3 and 1/2 inches of sand would be all that is required to stop a bullet since the standard distance between two pieces of drywall is about 3 and 1/2 inches.

How good of a defence is this sand coating really? How does it fare against armed men? What about primitive hunters? Natural predators?

  • $\begingroup$ What is your second quote from? Almost every major military in the world has tested their weapons against sandbags for over a century and I've never heard anyone suggest that the distance between drywall had a relationship with how much sand is required to stop a bullet. $\endgroup$ Oct 31, 2021 at 5:31
  • $\begingroup$ @KerrAvon2055 i believe its more a case of they had this convenient, available 3.5 inch spacing of rigid but otherwise completely non-bulletproof material, and filled it with sand to test. And yeah, 3.5 inches of sand will not stop a bullet. Not even a .22 short, al;though it will sap a lot of its energy. Read more about it here: concealedcarry.com/survival/… $\endgroup$
    – PcMan
    Oct 31, 2021 at 8:06

1 Answer 1


Smart sand with chemically induced ferromagnetism

We all know how you make magnetite "magnetic", by magnetizing it. But ... what if an organism creates a regular crystal of magnetite and other elements, capable of a strong magnetization, but it can magnetize it by a chemical reaction that flips the spin of all the electrons to a desired state at command from the organism? Now the organism has many semiautonomous grains that it can emit, which can align to attract or repel one another, converting the energy back and forth from magnetic potential energy to chemical energy storage as needed. These grains can assemble themselves into sharp little teeth - but bigger than a chiton's - and attract one another with substantial force. They can grip with blunt tabs or quickly scatter to the breeze - before homing in on their parent organism, perhaps with small gobs of flesh in tow. It is like a decentralized "muscular system" that can contract or repel in any direction, particle to particle. I think it should be reasonably fearsome, especially to the unsuspecting visitor from off-planet.


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