Orichalcum and You: Just How Good Is "won't break"?
 

"Orichalcum weapons won't break." (Adventurers p.106)

What precisely does this extend to? Exploits p.83 makes it clear that some nasty surprises (like gunk) can destroy an orichalcum weapon or shield (though it gets +2 to its HT, just like a very fine weapon), so they're clearly not wholly indestructible.

-If an orichalcum weapon is attacked directly (Exploits p.37), can it be damaged? Does it have more DR or HP than steel?
-How do Making and Breaking spells (Rive, Shatter, Weaken) interact with it?
-Can you melt it with the Heat spell? Is its melting point higher than iron or steel (which melt at the maximum the spell can achieve)?
-Will acid burn through an orichalcum lock?

Re: Orichalcum and You: Just How Good Is "won't break"?
 

The text is won’t break. Considering it’s a sort of Fantasy super-metal, for the purpose of DFRPG I’d stick with that. If the PCs find a broken blade, they should certainly poke through history books to find out just what broke it. Interestingly, this text isn’t mentioned for shields and armors, but probably because there are no breaking rules fir those.

Gunk damages it, ruins it, makes it unusable, makes it lose its unbreakability, but does not break it outright. Also, most if not all orichalcum equipment will be fine or better for at least HT 15. And Signature Gear. And Luck will be used to prevent breaking.

For the purposes of DFRPG, I would say Rive etc. don’t work.

I would let it melt just fine, not part of its job description. Acid I would resist with HT, maybe require more applications.

Re: Orichalcum and You: Just How Good Is "won't break"?
 

Orichalcum gear won't break due to major force – it's simply immune to kinetic damage, whether from blows, being dropped, or something else.

It is still subject to anything that corrodes or rots gear, but it gets +2 to the HT roll (Dungeons, p. 18). Not everything allows a roll to resist, so I'd take a page from the Shatterproof spell, and double DR and HP. Thus, a broadsword, normally DR 6, HP 11, would have DR 12, HP 22 against such things – including acid spells.

How other magic works depends on the GM's judgment. I'd treat Weaken, Shatter, Rive, and Explode as simply magical ways to deliver force, and thus ineffective. Ruin wouldn't do much just because it has no real effect on even ordinary metals that don't rust. I would let Disintegrate work, as it's a kind of corrosion, but I'd count DR and still double DR and HP.

Melting needs to be effective or how do you work the stuff? I'd treat it as no easier to melt than something that's exotic in a low-tech setting, and that's often used in steel in modern ones; e.g., chromium (3,380°F), titanium (​3,034°F), or vanadium (​3,470°F). Those just hurling Fire spells at it would once again encounter double DR and HP.

Re: Orichalcum and You: Just How Good Is "won't break"?
 

What's the Young's Modulus for orichalcum? Moh's hardness? :o)

Re: Orichalcum and You: Just How Good Is "won't break"?
 

Given Kromm's explanation, probably ∞.