These weapons are special in that they have four different leveled versions of themselves (level 1, level 20, level 40 and level 60). You can transform your weapon into one of these alternate versions by right-clicking it in your inventory and choosing "change".
To make the starfury weaponry, a starfire weapon and the required number of starborn diamonds have to be handed over to Ivar in the Artisans Workshop and he will smith a starfury weapon for you.
Making these weapons will provide you with 250 Mining XP.
Speaking to Ivar will take all of your starlight ore and starborn diamonds from your inventory and bank, and any weapons needed in the case of making starfury weapons. If you do not have enough of these to make the related weapon, the items will still be taken and you will be granted XP based on the items alone. Starlight ore will provide 5 Mining XP and starborn diamonds will give 2000.
If lost, the weapons can be reclaimed from Diango for a price.