|MadSci Network: General Biology|
Magnetite occurs within tissues of many organisms including human brain. In some animals it functions in magnetoreception, or the ability to sense the Earth's magnetic field. The function in humans is unclear, and since presence or absence of magnetite has no known medical implications, it has no been studied too much. I am fairly certain that if you studied it, you would find some degree of heredity - that is, a person with the trait would likely have parents and children also with it.
Try the links in the MadSci Library for more information on General Biology.