Interesting theory, but I've known several people who have removed this crystal, or at the least trained themselves to misinterpret the results.
Do humans have a compass in their nose? | The Register : Some years ago scientists at CALTECH (California Institute of Technology in Pasadena) discovered that humans possess a tiny, shiny crystal of magnetite in the ethmoid bone, located between your eyes, just behind the nose.
Magnetite is a magnetic mineral also possessed by homing pigeons, migratory salmon, dolphins, honeybees, and bats. Indeed, some bacteria even contain strands of magnetite that function, according to Dr Charles Walcott of the Cornell Laboratory of Ornithology in Ithaca, New York, “as tiny compass needles, allowing them [the bacteria] to orient themselves in the earth's magnetic field and swim down to their happy home in the mud”.
It seems that magnetite helps direction finding in animals and helps migratory species migrate successfully by allowing them to draw upon the earth's magnetic fields. But scientists are not sure how they do this.
(Tycho Brahe, astronomer, astrologer and alchemist, had a silver nose, or a copper one, depending upon the source you read)