 Because the magnetite is usually heavier than quartz, feldspar or other minerals, separation was usually done by washing it in sluice boxes (a method similar to gold panning but on a larger scale).Sluice separation typically yielded concentrations of magnetite ranging from 30 to 50%, depending on the type of sand and the method used.In the early 20th century a process of magnetic separation was developed that could produce concentrations as high as 70%.