About "Aluminium" & "Gold"

１st Gold is a very stable element, it seldom combine with other to form compounds. As it exists on its own, we can easily get this in nature, so it is found in early days(as there are little methods of extraction before)

２nd Aluminium is a relatively more active element(metal) it can combine with other elements more easily to form compounds. It exists as haemetite (a kind of ore) in nature,Al2O3.So an advanced technology is needed for extract the aluminium inside, electrolysis as this method is found later.



....Abundance of metal doesn't related to the year of discovery.

Gold is chemically more stable and hardly react with other elements. Pure gold can easily be found and can be seen easily by human eye. Thus gold can be found in early days.

Compare to gold, aluminium is rather active. It can react with other elements to form chemical compounds. Pure aluminium can not be found in nature. Chmical reaction is needed to gain aluminium. Thus it was found in late days.