Magnet
Rare earth (lanthanoid) elements have a partially occupied "f" electron shell (which can accommodate up to 14 electrons). The spin of these electrons can be aligned, resulting in very strong magnetic fields, and therefore, these elements are used in compact high-strength magnets where their higher price is not a concern. The most common types of rare-earth magnets are samarium-cobalt and neodymium-iron-boron (NIB) magnets.
Great Sand Dunes National Park and Preserve
The dunes contain dark areas which are deposits of magnetite, a mineral that has eroded out of the Sangre de Cristo Range. Magnetite is both attracted to a magnet and can be magnetized to become a magnet itself; it is the most magnetic mineral in nature. Magnetite is an oxide of iron which is heavier than the surrounding particles of sand. When overlying sand is removed by wind, magnetite deposits stay in place and are visible as dark patches in the dunefield.