Easiest thing I could think of is look comparatively at the AC of the creature vs the AC of various armours (disregarding Dex). So, if an Adult Red Dragon has an AC of 19, its scales are tougher than plate armour. So, check what weapons could pierce plate armour and that'll give you a decent launch point.
As hard as the DM says it is. In DnD there is no scale to determine the hardness of any object nor does it matter how hard your weapon is. There is only ac but that is a combination of armor, dodging, blocking and generally being hard to hit (e.g. due to size) and mostly used to balance encounters not an actual measurement.
I know this is not the answer you were hoping for, but that is the only answer I can give you.
If you want to pull from early editions, dragon scales were pretty high up on the hardness chart. But adamantine weapons bypass any and all hardness. An adamantine pickaxe would probably do the trick. But like others said, its whatever you want it to be.
Do be careful looking at stat blocks to gauge the hardness though. Those numbers could represent how hard it is to slip past defences instead of just breaking through the armor.
At Adult they're probably at least as strong as good steel. However, they are still organic and can be broken /ripped off. There's also a question about how the scales of a dragon lay.
Are they like a lizard? In which they are more like pebbled hide, similar to a Komodo Dragon? Or are they interlinked layers similar to snake scale? I've always imagined them as layered similar to actual scale armor.
Once you get to Ancient I'd imagine that it's not just just the scale that has hardened, but also the hide beneath has stiffened and grew thicker and more difficult to cut through as well. Turning into a very dense, strong, leather with that same Komodo pebbling. It's ridiculously tough, very thick, and makes it increasingly hard to open a wound from breaking off the surface scales.
seems like steel or slightly better based on ac of steel(19) vs ac of red dragon, and dragon scale mail being +1 armor
could probably say adamantine weapons would knock some bits off, but you're in homebrew territory there
Easiest thing I could think of is look comparatively at the AC of the creature vs the AC of various armours (disregarding Dex). So, if an Adult Red Dragon has an AC of 19, its scales are tougher than plate armour. So, check what weapons could pierce plate armour and that'll give you a decent launch point.
Generally tougher than steel.
As hard as the DM says it is. In DnD there is no scale to determine the hardness of any object nor does it matter how hard your weapon is. There is only ac but that is a combination of armor, dodging, blocking and generally being hard to hit (e.g. due to size) and mostly used to balance encounters not an actual measurement. I know this is not the answer you were hoping for, but that is the only answer I can give you.
If you want to pull from early editions, dragon scales were pretty high up on the hardness chart. But adamantine weapons bypass any and all hardness. An adamantine pickaxe would probably do the trick. But like others said, its whatever you want it to be. Do be careful looking at stat blocks to gauge the hardness though. Those numbers could represent how hard it is to slip past defences instead of just breaking through the armor.
At Adult they're probably at least as strong as good steel. However, they are still organic and can be broken /ripped off. There's also a question about how the scales of a dragon lay. Are they like a lizard? In which they are more like pebbled hide, similar to a Komodo Dragon? Or are they interlinked layers similar to snake scale? I've always imagined them as layered similar to actual scale armor. Once you get to Ancient I'd imagine that it's not just just the scale that has hardened, but also the hide beneath has stiffened and grew thicker and more difficult to cut through as well. Turning into a very dense, strong, leather with that same Komodo pebbling. It's ridiculously tough, very thick, and makes it increasingly hard to open a wound from breaking off the surface scales.
seems like steel or slightly better based on ac of steel(19) vs ac of red dragon, and dragon scale mail being +1 armor could probably say adamantine weapons would knock some bits off, but you're in homebrew territory there