[ArathornJax]

I don't see how the Arkenstone can be a Silmaril. First, the Silmarils were hallowed by Varda that no mortal hands or flesh unclean or evil could handle them but that they would be scorched. There are no exceptions here and dwarves are not like the Eldar, immortal, but only have an extended lifespan, and in the end, die as they are mortals.

Mandos said that they contained in them the fates of Arda, earth, sea and air were locked in them. And in the end, that is where they went into the earth, the sea and one placed in the air until after the final battle.

Based on this I believe that the Silmarils are found in the sky or air, in the depths of the earth and in the depths of the sea until the final battle. The Arkenstone is just what it is, a jewel that is beautiful and desirable but not a Silmaril.

What is interesting to me is the similarity between Feanor and Thorin. Feanor eventually begun to be greedy about the Silmarils, showing them only to his seven sons and his father, forgetting that the light within them was not his own. Thorin too, became very greedy with the Arkenstone, to the point of forgetting all the good Bilbo had done and wanting him dead. Why, because the Arkenstone was a Silmaril? No, but its beauty and power burned to his dwarven heart and his greed made him forget about the finer things in life. Unlike the Silmarils which drove the sons of Feanor to their deaths, the Arkenstone united the men of Dale/Longlake, the Elves of Mrikwood and the Dwarves of Erebor when Dain paid the debt for the Arkenstone and it was placed on Thorin in his tomb. Clearly for me, and others can dispute my belief and that is fine, IF the Arkenstone was a Silmaril, after defeating the Goblins and Wargs, the Elves, Men and Dwarves would have gone at it. That didn't happen (unlike the events at Doriath) and instead the Arkenstone is a great and wonderful jewel, an heirloom of Durin's folks and their kings, and it brought unity as Bilbo intended and nothing more. And for that matter, Bilbo did not scorch and wither after touching the Arkenstone several times (being mortal).

For me the Silmarils were not destined for this world to be seen until after the final battle . . . that is, unless Indiana Jones gets news of them and goes hunting them . . . then all bets are off.