Spinel is a mineral oxide of magnesium and aluminum. Its name comes from the sharp ends of its crystals which are reminiscent of thorns (spina in latin). It is a common mineral, formed at high temperatures as a complementary mineral in magmatic rocks, mainly basalts, kimberlites, peridotites and xenoliths. It also occurs in metamorphosed aluminum-rich schists and in contact metamorphosed limestones.
Pearls are lustrous and hard organic gems formed within mollusks, mainly in shells, around an original core, which can be either a parasite or a grain of sand. These foreign particles are then coated with layers of calcium carbonate. Pearls are thought to ward off negativism and clarify emotions. In the Revelation of John, pearls adorn the gates of the New Jerusalem.