A "diamond" is forever

[alatar]

First, the Silmarils had to be indestructible as a plot devise. If they were perishable, then Feanor could have destroyed them to spite everyone. Melkor could have done the same instead of bearing them in his Iron Crown. Or, when the War of Wrath was starting to go poorly for him, he could have then just smashed them. Melkor killed the trees; why not the Silmarils too?

And as stated, Feanor wasn't just thinking about Melkor, though I'm sure that stories regarding the same made him want to create something that even Melkor could not taint (as he had all of the rest of the works in Arda). Why not make something that might even confound Manwe or Aule? "Naa naa naa, I'm better than the Valar...Melkor defiled your works but not mine!" Iluvatar made certain things imperishable, and so why not Feanor? He was a little proud ya know...

And they had to resistant to Red Maw digestive systems.

And don't the jewels play some part regarding the end of the world, meaning that they would need to be (to borrow a word) null-entropic?

[Aiwendil]

Alatar wrote:

First, the Silmarils had to be indestructible as a plot devise. If they were perishable, then Feanor could have destroyed them to spite everyone.

Why on earth would he do that? Feanor loved the Silmarils more than anything else (the only possible exception I can think of being his father).

Actually, the Silmarils were destructible. After the darkening of Valinor the Valar asked that Feanor break the Silmarils and use the light trapped within to rekindle the Trees. And he refused. The point was moot because, unbeknownst to them at the time, Melkor had just attacked Formenos. But it remains true that even at the urging of the Valar, even to revive the Two Trees and reverse the Darkening, Feanor would not destroy the Silmarils.

The jewels came close to destruction again when Melkor quarreled with Ungoliant. Ungoliant desired to consume them but Melkor withheld them; this led to the Thieves' Quarrel. The arrival of the Balrogs prevented Ungoliant from consuming them, but the text (LQ2 I believe) clearly indicates that had Ungoliant consumed them they would have perished.

Finally, one may note that the Second Prophecy of Mandos foretells that at the end of the world the Silmarils will in fact be broken and their light will be used to revive the Trees.

So they were not indestructible. They were certainly difficult to damage or destroy, but not impossible.

[alatar]

Originally Posted by Aiwendil

Why on earth would he do that? Feanor loved the Silmarils more than anything else (the only possible exception I can think of being his father).

Just thought that Feanor, butcherer of Elves and burner of ships, would stop at nothing to possess/retain control of the Jewels. Assume that the Valar were going to take them by force, then I think that Feanor would have destroyed them.

Actually, the Silmarils were destructible. After the darkening of Valinor the Valar asked that Feanor break the Silmarils and use the light trapped within to rekindle the Trees. And he refused. The point was moot because, unbeknownst to them at the time, Melkor had just attacked Formenos. But it remains true that even at the urging of the Valar, even to revive the Two Trees and reverse the Darkening, Feanor would not destroy the Silmarils.

Was it that they could be destroyed, or unlocked/unmade? Maybe it's just semantics, but I can't see 'destroying' the Jewels to get the light out - though removing the light from the same would in effect 'destroy' them. Does that make sense?

The jewels came close to destruction again when Melkor quarreled with Ungoliant. Ungoliant desired to consume them but Melkor withheld them; this led to the Thieves' Quarrel. The arrival of the Balrogs prevented Ungoliant from consuming them, but the text (LQ2 I believe) clearly indicates that had Ungoliant consumed them they would have perished.

Not to quibble ( ), but IMO being consumed was not the same as destruction. Ungoliant would not have cracked them open with her teeth, but they would have been lost in the black hole of her appetite.

Finally, one may note that the Second Prophecy of Mandos foretells that at the end of the world the Silmarils will in fact be broken and their light will be used to revive the Trees.

So they were not indestructible. They were certainly difficult to damage or destroy, but not impossible.

Overall, I will have to agree with you in face of the evidence. Silmarils can be destroyed, but not very easily.