pickaxes work the same way as fishing rods and guns do
more info here
you can receive ores from crates or from mining, more so from mining with the use of a pickaxe. you are not meant to sell these ores, you can use the
$smelt command aslong as you have everything needed (furnace and coal - you can buy from
$shop). keep in mind that 1 coal is needed for every ore you want to smelt, and furnaces are one time use per command.
ingots and diamonds are items that you are meant to sell, you can sell them with