But limes are organic, so shouldn't limestone also count as organic?

…That's a salt, though, right?

If you're counting non-NaCl salts as answers, then basically any "mineral" our body needs would probably be delivered at least partly in salt form. Just reading off some multivitamins here:

• Calcium Carbonate
• Chromium Chloride
• Cupric Sulfate
• Potassium Iodide
• Ferrous Fumarate
• Magnesium Oxide
• Manganese Sulfate
• Sodium Molybdate
• Sodium Selenate
• Zinc Oxide

(I haven't fully checked all of these are salts­— But I mean, a lot of of them are blatantly chemical analogues of stuff that definitely is salt (E.G. "Potassium Iodide" vs. "Sodium Chloride"), plus they're metals bonded to ionic groups so they're definitely not alloys or covalent molecules or ceramics.)

This is probably because in order for our body to absorb stuff, it basically has be water-soluble, which means salts work quite well.

When eating real food (plants, animals, and fungi), I assume a lot of this won't be in salt form, but rather it will mostly be bound up in proteins and DNA and such. For example, iron should be primarily in hemoglobin instead of ferrous fumarate. But some of it, for example the potassium, will definitely be technically in the form of dissolved salts/minerals in the fluids inside the food.

You can of course also rearrange the compounds around. For example, this can of Windsor-brand "salt free salt substitute" I have here further lists:

• Potassium Chloride
• Calcium Silicate
• Magnesium Carbonate

You'll note that these are some of the same components as in the list above, just a different combination. I'm pretty sure any ionic mineral that includes at least one ion that our body needs technically counts as "food", as long as the other half isn't poisonous— They should be basically the same when they dissolve in the water in our stomachs anyway.

Meats can also be preserved by adding nitrates and nitrites to it, though technically I guess that's more of a likely-carcinogenic additive than part of the "food".

Fun fact: Your body sorta knows when it's low on minerals, and will want to start eating dirt and rocks in order to make up for it! Over 100 different types of primate do it too. So in that case, you could probably argue that plain rocks and soil literally are food, in that they provide vital nutrients the body needs and that your brain is smart enough to know that. …These days it's apparently considered a mental disorder, but I swear it made much more sense back when the likeliest thing you were going to eat was some mud, rather than lead-contaminated radioactive refrigerants or whatever it is we've surrounded ourselves with.

Enjoy, also, this lovely video from a chemistry Youtuber and his friends taste-testing which alkaline-chloride salt tastes the best!

I am not a doctor. Don't go around eating rocks unless you're a bird or some other type of dinosaur.

FWIW, most of our use of it comes from organic sources I believe.