Tin

"RealClearScience" is doing a series on the elements, including today's "tin."  This kind of thing is always interesting, but something I particularly enjoyed was reading that the first bronze may have been stumbled on when people made an accidental alloy from ores that naturally contained a suitable mixture of copper and tin, perhaps as early as 5800 B.C.  I'd always thought of the Bronze Age as beginning around 3500 or 3000 B.C. Of course dates for these things vary considerably over the world, and it shouldn't be too surprising that the idea crops up here and there quite early before it grabs hold and spreads.  It was a long time before cultures became complex enough to transmit this innovative idea reliably from generation to generation, then from place to place, and also to allow a robust trade in tin over continental distances.  Even slower, perhaps, was the cultural development that favored systematic experimentation with fussy recipes for alloys and counterintuitive stabs in the dark like different quenching methods.