RDD please check your facts.
Magnetite Fe3O4
Atomic mass of iron Fe 55.8450
Atomic mass of Oxygen 15.9994
Atomic mass of FE3O4 =(55.845x3)+(15.9994x4)=231.511
Maximum % of Fe in Magnetite Fe3O4 is 72.3%
74% Fe "cake" impossible.
Concentrates typically average around 68-70%, too much energy required to do better.
RDD is exaggerator. Be careful.