On the bank of Mures River in Transylvania, near the city of Aiud, in 1974, an aluminum wedge was found among 20,000 year-old Mastdon bones, encased in one millimeter thick layer of oxides that shows it to be at least 300-400 years old. Aluminum is always found mixed with other metals but it was pure aluminum. 

This 300 year old artifact is anomalous because aluminium was not discovered until 1808 and not produced in quantity until 1885. It’s still under research at an undisclosed location.

SOURCE : BEFORETIMES.COM