You can see no flaw in the tusk. A tusk such as this might command coin from Men or admiration from the dwarves, but in the hands of an Elven weaponsmith this tusk could become a deadly weapon. A weaponsmith of sufficient skill might dwell in Rivendell.
Your encounter with a ferocious boar not far from the Great East Road yielded a boar-tusk of surprising strength and beauty.
An Elf weaponsmith in Rivendell might be able to craft the boar-tusk you obtained into a deadly weapon.
Rivendell might be the home of a weaponsmith able to work with the boar-tusk you obtained.