I looked it up to check your claim «Unfortunately, the substance can't be gold. It's too light by a good margin.»: Au's density is 19.3, Pu ’s density is 19.8. It's not significantly lighter. It also doesn’t look like gold, and will tarnish once exposed to air.

I don't think Composition B will explode by any means the assistant has available. It will just burn. On Mythbusters they showed Comp-C actually doesn’t work as well as Sterno for cooking. They have no concept of explosions.

@JDługosz , you are correct about plutonium. But nuclear weapons use a different "kind" of plutonium, delta-phase plutonium (alloyed with gallium to stabilize it), which has a density of 15.9. It will still tarnish once exposed to air, and that's why it's nickel-plated and the nickel then covered in gold. About Composition B, well, you caught me there and no mistake :-). It's possible to cook Comp-B off and trigger an explosion, but that's not likely to happen inside an athanor. A mortar-and-pestel setup also isn't likely to do anything.

It would be cool if you could include some links for that. BTW, in high school a friend made some RDX, and the pure powder does explode when set off with some waterproof cannon fuse.

Implausible, as is stated, but well written, fun to read and seemingly good, solid facts.

@JDługosz "Comp-C actually doesn’t work as well as Sterno for cooking." Yeah, most people wouldn't be surprised by that. For the wrong reason, sure, but... ;-)

I do like this. It would take a genius of an alchemist, lots of luck and intuition, and much more (handwaving aside), but the logic and tread are tightly woven which takes some doing. Kudos.

Sounds like the same alchemist who weaponized Uranium in this answer of mine from 2 years ago.

I like it, because like much of real life alchemy, the result is correct, but the logic chain is completely ridiculous and wrong.

Where did you get all that improbability from? must have costed a fortune

I didn't understand the end: is the A-bomb going to explode when opened?

@BЈовић No, it'll just spread cancer everywhere.

"[...] this thing was designed for, and capable of, flattening a city" - and there he would possibly underestimate it's power, if you look at what "city" means now, compared to medieval cities. Nice story, enjoyed reading it.

@Edheldil Boosted weapons have a hollow core into which tritium is injected. There wouldn't be a removable plug, though; the tritium is pumped from a separate reservoir as part of the arming process. This also allows the yield to be adjusted, by injecting more or less.

Check out the ST:TNG episode "Thine Own Self" for some ideas on how the investigation might progress.

@LSerni Don't forget, a few days (if he's lucky) after pulling out the "Philosopher's Stone" at the core the alchemist in question starts having severe digestive problems, hair loss, bleeding from unpleasant places, etc. It doesn't end well for him.

Explosives are usually organic chemicals containing many nitrate groups, which have a tendency to decompose into less stable chemicals, especially if not stored in ideal conditions. Composition B might once have been very well behaved, but after centuries of burial ... I think the alchemist may be lucky it did not blow him up as soon as he started scraping at it!

Did you really had to use that small text? Just wrap it in a spoiler tag if you don't want to disrupt the flow of the narrative. But don't abuse markup for what it was NOT intended to be used for.

@Mindwin , done. I'm afraid I did the small text trick in some other answers, I'll see if I can hunt them down. Thanks for the suggestion.

@LSerni we, sighted and well-coordinated literate people usually design things for other sighted and well-coordinated literate people. At the expense of those others that require accesibility tools.