New evidence for the Arkenstone-Silmaril case

[Inziladun]

Originally Posted by Puddleglum

The Arkenstone was already seen as the rightful property of the Dwarves (except for Bilbo's claim to take it as his "rightful" payment for coming on the quest). Even if it "were" a Silmaril (which I don't believe), Gandalf wouldn't have popped in and said "The Sil's are the rightful property of the Valar" (they never were in the first place) "so I'm going to take this from you and deliver it". Fate (Providence, if you wish) had already placed the Arkenstone where it was, and the Dwarves had unearthed and shaped it on their own. The Valar would have respected that.

While the Silmarils weren't the responsibility of Gandalf or any of the Istari, I don't think it likely Gandalf would have allowed one to remain at Erebor.
Look at all the mischief they caused in the First Age. They seem to have engendered a lustful desire to possess them almost on the level of the One. Even old Elwë couldn't resist the lure.