That is a tibia and fibula from the right arm of an alien, which was shot down by natives.
It obviously crashed in the Upper Peninsula of Michigan near natural copper deposits.
The eventual leaching of groundwater infused with copper molecules over millions of years caused calcium contained within the bone structure to be displaced and supplemented with copper.
The bones were most likely found after the glacier receded and traded to French fur traders, making their way down the Mississippi via canoe on the Lake Michigan Shore, then traded to Spanish Missionaries visiting Louisiana.
The missionaries in turn took them to Mexico. they were given to and carried by members of the battalion Saint Patricio, due to their reddish color.
Where they were lost in a raid by American Forces.
Outnumbered and outgunned, the members of the battalion buried them before they died.
And you dug them up.
Seriously, though. Do you have a size reference?