Dragon's Flame, Magical?

[The Might]

About the mail, considering that it has to be heat resistant I think it also has a lot to do with what it is amde of and not how it is made.
What about a heat resistant alloy?

It seems that gold melts at 1064°C so that is pretty much what you would need to destroy the One Ring.
Superalloys that are not only quite heat resistant but also have great mechanical strength (making them good for armor) take up to 1100°C.

What if dragons were only capable of lesser temperatures? That is an explanation I believe.


About the dragons, yes, there certainly were some left.

And finally about their origin.
In the Silmarillion they are presented as a corrupted stock, another of Morgoth's creations like the fell beasts the Nazgul used in the War of the Ring.
However, in a later passage from the Children of Húrin they are called "great spirits", which kind of implies that they, or at least some of them, might be fallen spirits, similar to the balrogs.