Do gems dissolve in acid?

[Celebrim]

This is one of those questions that depends alot on whether you are using fantasy acid or realistic acid.

Fantasy acid has one attribute - potency. The more potent it is, the more things it disolves and the more material it disolves relative to its volume. Fantasy acids can disolve objects having several times there own volume. Fantasy objects resist all acids equally. Either the acid resistance is high enough to resist the acid, or it is not.

Realism is much more complex. Probably too complex.

Let's suppose Al is right, and Black Dragons produce hydrocholoric acid or at least its equivalent (which is weird, because Chlorine is not an element; where is the Elemental Plane of Chlorine?)

Some gems will do alot better than others.

Diamond is fairly impervious to acids of all sorts. However, it can be made to burn in the presence of certain oxidizing agents.

Corundum and most of the other aluminum gems (like Alexandrite and I think Garnet) are essentially impervious to acids.

After that, it gets complicated. Peridot will disolve almost instantly in hydrocloric acid. Topaz on the other hand is unaffected by hydrocloric acid, but will be disolved by nitric adic. Hydrofluoric acid will disolve opals, aquamarines, and amethyst.

 

[Alejandro]

Why not use the object hardness rules? Stone has a hardness of 8, so the dragon can store them in 1d6 acids without fear.

 

[radferth]

Who knew there were so many closet chemists here. Remember that in the game context, and chemical attack is treated as acid, so things like a green dragon's chlorine breath and basic substances like lye do "acid" damage. When I am running (and my players can testify I use an irritating amount of real world science at times) I use the following rules.

1) In game "acids" are assumed to be run-of-mill acids or bases unless otherwise specified (e.g. no HF).

2) Gold, platinum, glass, ceramics, and hard gems (diamonds, rubies, saphires, etc) are assumed to have huge amounts of acid resistance (virtual immunity).

3) Silver and copper are fairly acid resistant, but not immune.

4) Assume an alchemist of enough skill could divise a solvent that inflict "acid" damge on just about anything, or even one that is selective (e.g. metal but not wood or flesh, stone or flesh but not metal, etc.)

To answer the original inquiry, yes, I'm sure a black dragon could drool out acid the right strength to harm characters and the equipment, but not diamonds and rubies.

 

[Number47]

That would be up to 1d8 without harm. You can and certainly should rule that diamonds have a higher hardness. I'm not sure if rubies should have a higher hardness than stone, but you could say 10 without getting too much argument from most people.

According to the rules, acid does full damage to objects, yes? I don't have the rulebooks in front of me. I know that fire only does half...

 

[Alejandro]

Oops, acid does half damage to objects. So, rinsing gemstones in a vat of 2d8 acid is just fine.

 

[Number47]

...or more if you up their hardness to more than 8...

 

[Kibo]

That would be up to 1d8 without harm. You can and certainly should rule that diamonds have a higher hardness. I'm not sure if rubies should have a higher hardness than stone, but you could say 10 without getting too much argument from most people.

Considering the etymology of adaminite/tine/antium diamond should have the hardness of whichever one of those your campaign uses.

 

[Alchemist]

Let's suppose Al is right, and Black Dragons produce hydrocholoric acid or at least its equivalent (which is weird, because Chlorine is not an element; where is the Elemental Plane of Chlorine?)

Being a not-so closet Chemist, I can tell you with great degrees of certainty that we consider Chlorine to be an element. It's number 17 on your periodic table.

I would just KISS and say gems are impervious to such things.

 

[Al]

Alchemist, I assume that Celebrim was referring to Chlorine not being an Element (as in, no Chlorine Elementals) rather than an elemen (i.e. chemical element). Although annoyingly enough, there are no acid elementals either.

Back on the main topic, the issue of acid damage vs. hardness is fine if you use a 'fantasy acid' model. Using a 'realistic acid' model, it is more difficult. All acids have a 'maximum' strength (usually around 17M), so if the gemstone won't dissolve in that, it won't dissolve in any form of (that particular) acid, no matter what the damage. Conversely, gemstones subject to reaction with certain acids will usually go if the damage is significantly less. The damage itself could be explained by quantity of acid in combination with molarity (strength), so a 100 point breath weapon could simply be twice as much volume as a 50 point breath weapon without actually being 'stronger'. Unfortunately, this flies in the face of 'acid resistance'- which, if working in real chemical terms, can resist 1 litre of acid pretty much as well as 10 litres, assuming they are the same strength.

Given that this is 'fantasy' though, and given the parameters implicit in acid resistance, it's probably just easier to use the damage/hardness routine. DnD is a game, not a chemistry lesson.