They are actually not useless
They serve for making Infused Sling bullets ( preety much adding special properties to bullets the same way arrows have ) . I must say that its way too expensive to go this way ( believe me i know after had trained 2 slings to unlimmited ammo ).
For the said bullets you need one enchanted ingot, one enchanted gem ( fire opal or ruby ) and one piece of a mushroom ( which add the kind of damage ).
Now Nwn seems to consider that something enchanted is way less worthy that something in raw materials. The gems acts on the same way. That goes regarding the "price" NWN sets upon the items not sure if something can be done about it.
JC / Redeemer