Indeed. The chemical properties of the elements will make some easier to extract than others. Metals that have been known since prehistoric times (copper, tin,

Indeed. The chemical properties of the elements will make some easier to extract than others. Metals that have been known since prehistoric times (copper, tin, lead, silver, zink and others) easily combine with sulphur in the crust, and can be found as easily extractable ores, while the rare earths are as abundant as these, but do not concentrate much in specific ores. The same goes for Uranium, that is surprisingly common in most minerals. What matters is how easily the elements can be extracted and processed. Aluminium is 13% of the crust by weight, but was not possible to process before after around 1880, because electrolysis and large scale electricity production had to be in place first.