Why were the Silmarils so important?

[Knight of Gondor]

Yes, I'd say the pride of the sons of Feanor played a large part. They were a token of his works, and his sons were jealous to keep it in the family. Just another way Melkor marred the original harmony of the original Creation.

[Orophin]

I agree with those that say that the pride of the sons of Feanor and Feanor himslef are the main cause for the war. But when you think about it, these jewels are beyond price. The obviousley can't be made agin or else Feanor would have just made more. These things represent everything that Feanor worked for and his pride so when they were stolen from him he went nuts, and his sons followed him.

[luthien-elvenprincess]

The story of the elves' dealing with the Silmarils show us that elves had some of the same basic flaws as men. Elves tended to disdain men for their lust for power (which some men certainly had, but not all). Yet, the story of the Silmarils show us that elves also had a problem with lust (again, some elves, not all).
It is interesting to note that the Valar suffered the same loss as the elves, yet didn't react in such a manner as to bring sorrow and grief to the world.

[Voralphion]

As to the silmarils having any power, it is said that the elf colony at Tol Sirion where Earendil left from was made green by the power of the Silmaril of Elwing that brought healing. Although this was attributed to the Elessar in another version of the story, the silmaril did have healing powers.

[dkhyrosha]

I think it was a combination of the killing of Finwe, the pride of Feanor, and the fact that the light of the jewels was all that was left of the Trees

[bilbo_baggins]

Maybe not so much the loss of the light of the Trees...

Weren't the Trees detroyed and then the Valar made an appeal to Feanor to give of his Silmarilli to return life to the trees? Feanor turned them down and returned home, only to find that his precious jewels had been lost. Then Feanor went a rampage of vengeance and retrieval. Feanor cared only for his creation, and he was the main instigator of vengeful thoughts among the Elves of Tol Sirion.

That's just my thoughts,

[Frodo2968thewhite]

it is true that the Elves cherished the jewels for the fact that they hold the last light of the two trees, but Fate also must have played a huge role in it...The way I see it, everything that happens 'in any world' is for a reason. I do believe that Arda once existed, and that Iluvatar must have had a plan for the Silmarils. It's not just the physical power that they beheld that is amazing, but also the spiritual aspect of it. Let us go to the second prophecy of Mandos...

Thereafter shall the Silmarils be recovered out of sea and earth and air; for Earendil shall descend and yield up that flame that he hath had in keeping. Then Feanor shall bear the Three and yield their fire to rekindle the Two Trees, and a great light shall come forth; and the Mountains of Valinor shall be levelled, so that the light goes out over all the world. In that light the Gods will again grow young, and the Elves awake and all their dead arise, and the purpose of Iluvatar be fulfilled concerning them. But of Men in that day the prophecy speaks not, save of Turin only, and him it names among the Gods." (The Shaping of Middle Earth - HOME 5)

So from this I conceive the fact that The Silmarils were important because of fate and roles that they have yet to play...