A very uniform grade of iron ore is known to be entirely formed from a mixture of different oxides of iron (iron oxide FeO, magnetite Fe$_3$O$_4$ and hematite Fe$_2$O$_3$), although their ratios are not known.
$1$g of this mixture is fully reduced, leaving $0.748$g of pure iron.
Must all three of the oxides indicated be present in the mixture?
Is there a smallest or largest amount of each oxide present?
What possibilities for the percentage composition of the mixture by mass does the experiment indicate?
Can you create a yield of iron which would prove the absence of at least one of the oxides of iron from the ore?