Like The One Ring, I think Silmarils were indestructible (by others than the Valar and Fëanor himself). But as "what happened to them", they would get destroyed yet - with the help of Fëanor himself, surprisingly enough. See the prophecy of Dagor Dagorath (Battle of Battles) for those answers.
But it is an encouraging thought that he would repent eventually, and make it up for it all.
Last edited by Lindaelle; Dec 24 2012 at 04:21 PM.
'There now the numbers of Eldar increase,' Voronwë said, 'for ever more flee thither of either kin from the fear of Morgoth, weary of war.'
In Laurelin - Lover of Tolkien's lore