[Gregstrom]

To add to Scarlioni/analytic_kernel:

Arsenic is certainly found near tin - I couldn't say if it's found near copper. It is IIRC easier to refine from ores than tin, which might help explain why it was used first.

Also, IIRC bronze is harder to recycle than iron. I have heard that recasting bronze has a bad effect on its quality, making it harder and more brittle - not a terribly good thing for armaments. Damaged iron items may be readily reforged though.