Where are rubies formed?
Ruby, a variety of the mineral corundum, is formed as a metamorphic mineral associated with regional and contact metamorphism. Contact metamorphism involves the exposure of pre-existing rock to high temperatures from close proximity to magma underground at various depths. Regional metamorphism is due to intense pressures and varying degrees of heat due to the compressional force of tectonic plate collisions, and is usually a deep underground phenomenon.