[Formendacil]

I think it is oversimplistic to think of the fires of Orodruin as the Secret Fire. As with most, it would seem apparent that the Secret Fire is not to found in something so mundane as a volcano. (Let's face it, Melkor couldn't find it in the Void, could he?)

And while bringing this up does stray a bit from the topic (ie. the Chapter) at hand, the original question that brought it up comes back to my mind: What was it about Orodruin that made it so dangerous to things like Rings and Palantiri?

In the case of the Ring, the fact that it was the place of its creation would seem to be reason enough. A sort of a full-circle effect. It was made here, so it can be broken here.

But why was Orodruin selected as the place of the Ring's in the first place? Sauron seems to have definitely had a reason. Furthermore, how does it figure in as being destructive to the Palantiri?

So here's my hypothesis:

In Morgoth's Ring, in the part that gave the book it's title, it tells of how Melkor suffused his power into the hroa of Arda, how Arda became his Ring, prefiguring Sauron's later act with the Ring.

In this part, it says that there is a Melkor-element in all the physical matter of Arda, but that it is there in varying degrees. Silver and water are singled out as being almost unstained by the Melkor-element, whereas gold seems to have been much more heavily concentrated with it, hence Sauron's use of gold to create the One Ring.

Perhaps the Melkor-element in Arda is not only stronger in certain elements, but also in certain places. My theory is that Orodruin was home to a very strong concentration of Melkor-element, which made it very destructive (hence the ability to destroy things otherwise close to unbreakable, eg. the Palantiri), as well as logical place for Sauron to seek out. After all, if he deliberately chose gold as the material for the Ring because of its strong Melkor-element, then it surely stands to reason that he would chose to forge it in a place with a strong Melkor-element.