In my world (based on D&D) orcs are a pre-metalworking society that clash with various agricultural humanoid civilizations. However, I would also like them to have metal weapons so they are a plausible threat to metallurgic civilizations, and I don't think that 'theft' is a good explanation.
Then, I realized I might be able to solve this problem in a way that ties in to other pre-established traits (high mortality rates, orc resistance to injury). What if the structural component of their bones isn't carbonated hydroxyapatite, but something different? I read a post which suggested that the issues of bone are that it doesn't hold an edge and tends to fracture easily: are there alternative molecules that don't have this problem?
Basically: is there a mineral that could plausibly be produced by biological processes, that'd serve as a structural component for bones, and that orcs could turn into workable spear tips and axe blades after extracting it from the fallen?