merging this tin with their copper to create sturdy tools and weapons, even ones capable of breaking bronze
You may be slightly mistaken. I believe that merging tin with copper is the very way to create this "bronze" you speak of.
Our village also obtained some "eye-yearn" (similar to your eye-rown?) from a travelling merchant last year. We have been attempting to replicate it by merging varies quantities of copper, tin, and silver, but without success. We are beginning to suspect that it cannot be created through merging, and must be extracted with a process or ore unknown to us.