Diamonds are carbon crystals formed deep under the Earth under tremendous temperatures and pressures. Diamonds, on the other hand, are metastable; they will not decay into graphite under normal conditions due to an extremely strong kinetic energy barrier. However, radiation can break down diamonds, forming gas within them that can collapse under its own weight, turning the diamond into graphite. The half-life of diamonds has been estimated to be between 1030 and 1090 years. This means that around 0.7% of all diamonds should have decayed by now. The vast majority of diamonds, however, are too small to be seen with the naked eye, so they remain hidden in sand or gravel where they cannot be detected by human observers. Decay is a process that involves loss of mass through any pathway. In the case of diamonds, they lose mass through radioactive decay. Specifically, they decay via beta minus emission, which results in the production of helium and tritium. Helium is less dense than oxygen (and thus more buoyant) so it floats away from the diamond, while the tritium remains trapped inside because it is inert. Over time, this leads to a reduction in the density of the diamond and it will become susceptible to further erosion. Decay is only one factor that determines the rate at which diamonds are removed from the ground.