[The Might]

Hmmm good point there Alfirin, I was not aware of that and under the circumstances of Tolkien's studies it does seem to be a lot more plausible that actually he had been considering the European legends about meteorites when he thought of Eol's story.

And yes, the black stone of Erech does intrigue as after all it was nice, black, round and shiny but it wasn't a palantir, just a stone in the end. Maybe Isildur liked shiny rocks?