: I got the impression that most mithril was hoarded by Sauron in Barad Dur. I think it is safe to say that when the tower was destroyed a great deal of the mithril was destroyed too. As for Moria from what I have heard it was almost mined out by the dwarves just before they found Durin's Bane. Tolkien mentions once that as the Middle-Earthian society decayed the differant races grew in their mistrust. Men with their greater numbers eventually destroyed the dwarves in a greedy attempt to steal the hard earned wealth of the dwarves (I think this is hinted at in the appendix to LoTR).

: Thorin

I don`t think we know that the mithril itself is indestructible - all we know is that you can make from it a metal that is far stronger than any other. That metal is not pure mithril, which, I suppose, might not be indestructible after all.

Nor do I think that Sauron merely hoarded it. It was far too useful, and Sauron wasn`t a jackdaw like Saruman. His personal armour would have contained it, I`m sure (we know from the letters that he was clad in mail), possibly that of some of his chief servants (not sure about the Nazgul) and anything else he wanted to be sufficiently strong. I think it is likely that Grond contained it: it would have given it an advantage over gates of steel, and it is possible that the new gates that were made for Minas Tirith after the war "of mithril and steel" actually contained mithril recovered when Grond was melted down. If the gates of Minas Tirith in the Fourth Age were to contain mithril, then it is probable that the gates of Barad Dur had contained it also, and possibly the black gate too - we are, after all, told that it was stonger than any siege engines Gondor could provide. After his lesson at the end of the Second Age, Sauron did not skimp on his own security.

There were probably lots of things Sauron could find it useful for, that we know nothing of. As a former Maia of Aule (and probbaly the most powerful) Sauron must have been little Sauron didn`t know about its properties. It`s possible that it could be used in his sorcery: the elves made ithildin of it, which only reflected moonlight, and then only when certain words were said - it sounds as though they could put their magic into it.

Also, while Sauron principally collected wealth and tribute from his vast realms in the east, it`s not impossible that he gave out gifts and treasure too, on occasions when it served him to, and to buy influence over very distant peoples.

I`m not a scientist, and so I have very little idea about what mithril might actually be. We`re told that in Middle-Earth it only existed in a single lode that led north deep under the mountains of Moria, but that it also existed in Numenor, and, I imagine, in Aman as well. Could it be some incredibly rare element that doesn`t exist in its natural form, that in modern times is used to strenghten steel, but which requires unbelievably high temperatures or certain conditions to be obtained in its pure form? It would probably be rather heavy, but it`s only the metal, or alloy, that`s made from mithril that`s light, not neccessarily the pure substance itself. How it could exist in a useable state in Moria I just don`t know, unless it were a feature of how the Misty Mountains were made; unlike all the other mountain chains, they were thrown up in geologically recent times by Melkor to hinder the elves.

Alexander