Magnet
Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states, as ores. These include iron ore (magnetite or lodestone), cobalt and nickel, as well as the rare earth metals gadolinium and dysprosium (when at a very low temperature). Such naturally occurring ferromagnets were used in the first experiments with magnetism. Technology has since expanded the availability of magnetic materials to include various man-made products, all based, however, on naturally magnetic elements.
Perovskite (structure)
The most common mineral in the Earth is bridgmanite, a magnesium-rich silicate which adopts the perovskite structure at high pressure. As pressure increases, the SiO tetrahedral units in the dominant silica-bearing minerals become unstable compared with SiO octahedral units. At the pressure and temperature conditions of the lower mantle, the most abundant material is a perovskite-structured mineral with the formula (Mg,Fe)SiO, with the second most abundant material likely the rocksalt-structured (Mg,Fe)O oxide, periclase.