I have a few organosilicon characters, and I like to know how things work. Some of these types of creatures make shells, but others just reinforce their organic flesh with the silicon.

According to my brief research, silicon exposed to oxygen makes something that is hard to break the bonds of, and that glass can be broken down by some chemicals containing fluorine. So this creature's digestive system would probably contain fluorine. What would be the best fluorine containing chemical for this?

But how does the carbon component of this creature affect this? Would the fluorine containing substance impact the organic bits negatively, and if so, how do I get around this?

Edit:I may have misunderstood something somewhere, but I meant breaking the silicates down enough for use, but not necessarily separate it from the oxygen. I read hydrofluoric acid makes the fluoride combine with the silicon, which I do not want.

  • $\begingroup$ you may want to look at glass sponges which build a silicate skeleton. $\endgroup$
    – John
    Mar 7, 2021 at 20:49
  • $\begingroup$ @John but don't those filter particles of it out of the water instead of breaking rocks into small enough pieces? $\endgroup$ Mar 7, 2021 at 20:54
  • $\begingroup$ Of course, why break down rock when it is already broken down into a soluble form for you. Plants break down silicates with acids. $\endgroup$
    – John
    Mar 7, 2021 at 20:56
  • $\begingroup$ @John by breaking down silicates do you just mean smaller chunks or like the hydrofluoric acid that removes the oxygen from it? $\endgroup$ Mar 7, 2021 at 21:00
  • $\begingroup$ Plants break it down using salicylic acid and carbonic acid to break down rock into a soluble form (AKA dissolve it), silicic acid Si(OH)4. there really is not much reason to try to isolate the silicon atoms. you don't digest meat by turning into individual carbon atoms/ions. $\endgroup$
    – John
    Mar 7, 2021 at 21:04

4 Answers 4


You do not need to break the silicon oxygen bond.



You are right that SiO2 is hard to break. But your creatures can use the silica molecule (silicon and oxygen) as a unit. They can build things out of those units. Depicted: radiolarians, who build an impressive variety of shells and hard structures out of opaline SiO2, which they take out of solution. https://ucmp.berkeley.edu/protista/radiolaria/radmm.html

Radiolarians could be considered organosilicon creatures. Your creatures can use the SiO2 building block to make teeth, shells, scutes, bacula, or whatever your story requires.

  • $\begingroup$ Oh, I mistakenly messed up the wording. What I meant was breaking silicon oxygen bonds from other silicon oxygen bonds, as this creature eats big rock chunks, not collecting particles from water. $\endgroup$ Dec 23, 2020 at 20:39
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    $\begingroup$ @ChickenpeepChickenpeep there is still no reason to break it down into individual silicon ions, you don't digest meat and sugar by breaking them down to individual carbon ions, you just break them down into a soluble form. salicylic acid and carbonic acid can do that to silica. $\endgroup$
    – John
    Mar 7, 2021 at 21:12
  • $\begingroup$ @John I need some more information to tell me how it works. $\endgroup$ Mar 7, 2021 at 21:22
  • $\begingroup$ @ChickenpeepChickenpeep - Imagine you are making rock candy. You dissolve sugar crystals into a water solution. The sugar molecules are loose in solution. Then you let it crystallize back out of solution into the rock candy. Radiolarians are doing that with SiO2 and more control over how the crystal forms. They capture silica that has already dissolved and crystallize it into their shells. Your creatures do the dissolving part too by eating rocks and dissolving them down to SiO2 molecules. $\endgroup$
    – Willk
    Mar 7, 2021 at 21:54

Well, if our stomach uses HCl, chlorhydric acid, to digest food, your creatures could go with HF, fluorhydric acid, to break down silicon based molecules. Despite being a weak acid, it's still highly corrosive.

And as our stomach cells are protected by self digestion from a layer of mucus, the same can happen for their stomach.

The creatures can use a mixture of HCl and HF, or have two stomachs, one using HCl and one using HF.

  • $\begingroup$ or salicylic acid or carbonic acid which are not nearly as hard to deal with chemically. $\endgroup$
    – John
    Mar 7, 2021 at 21:18
  • $\begingroup$ Alternative go alkali instead of acid and then you can just use sodium or potassium. which is easier and a LOT faster. $\endgroup$
    – John
    Mar 7, 2021 at 23:26

Go alkali instead of acid.

Then KOH is enough. This is far FAR less toxic to biological systems.

As a bonus potassium is something already sourced from rock and biology uses in abundance.

Or you can use sodium instead. you need a lot more heat though.

Or in just water you can use molybdate (MoO4) and phosphate, this however is slower than the other methods.


What would be the best fluorine containing chemical for this?

Fluorite is the most common one on Earth, I believe. It isn't too unusual, but it is generally found underground rather than in surface deposits.

Would the fluorine containing substance impact the organic bits negatively, and if so, how do I get around this?

Oh, very badly! Hydrofluoric acid is astonishingly nasty stuff. You keep it in containers made from fluorine compounds such as teflon. Anything that's not a fluorine-based compound just isn't oxidised enough, and the HF will eat it.

You might get away with some kind of mucous layer in the stomach and digestive tract, but as it would react with the HF you'd deplete your store of the chemical sooner than you'd like. I'm not sure what kind of organic fluorine-bearing polymer your beasties could use, but you could pick almost anything as they already have clearly pretty weird metabolisms.

I meant breaking the silicates down enough for use, but not necessarily separate it from the oxygen. I read hydrofluoric acid makes the fluoride combine with the silicon, which I do not want.

Oh. In which case don't use HF at all, because you'll lose it.

Just produce some suitable biomineral for claws and teeth and crop or whatever that's just harder than silicates. Something like corundum or carborundum would do. Other questions on this site discuss biosynthesis of superhard minerals. This news article mentions bacteria that can do it. Chomp up the glass and redistribute it like any other nutrient and deposit it appropriately. Job done!

As an alternative, you might consider a basic, rather than acidic digestion using nice hot sodium hydroxide to dissolve quartz and form sodium silicate, commonly known as waterglass. It is a useful compound by itself, but when put in a suitably acidic environment you can precipitate the silica back out again.

This requires some fairly unusal biochemistry and a fairly energetic digestive tract, but TANSTAAFL!

Now you know why plants and marine diatoms make their silica from silicic acid they get from the environment, instead of having to do it the hard way like you want.

  • $\begingroup$ Oh that's good. I assumed that silicate stuff would require some digestive enzyme we don't have. $\endgroup$ Mar 7, 2021 at 20:43
  • $\begingroup$ @ChickenpeepChickenpeep it really depends on what you want to do. Producing a kind of bioconcrete from silica powder would be relatively straightforward; growing a quartz shell would not. $\endgroup$ Mar 7, 2021 at 21:22
  • $\begingroup$ what exactly would bioconcrete mean? What are its strengths and weaknesses? $\endgroup$ Mar 7, 2021 at 21:27
  • $\begingroup$ @ChickenpeepChickenpeep something made with ground up silica glued together with protein, as an analogue to regular concrete which is ground up rock stuck together with cement, more or less. I've no idea what its properties would be offhand. Its just a throwaway idea. $\endgroup$ Mar 7, 2021 at 22:19

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