Glassy form of carbon can transform into diamond

National Geographic : A glass-like carbon allotrope that’s been used for 30 years in chemistry and electronics has recently been found to become hard as diamond under high pressures. Ho Kwang Mao, of the Carnegie Institution of Washington, and colleagues slowly applied pressures—similar to those found hundreds of kilometers below Earth’s crust—to the allotrope, which under normal conditions is made almost entirely of flat bonds, like graphite. Under pressure, the bonds changed from flat to three-dimensional and crystalline, which gave the substance a diamond-like hardness. When the pressure was released, the material returned to its pliable glassy form, its bonds flat once more. Although it’s too soon to know what commercial uses could be found for the reversible carbon, it could potentially be used in laboratories to apply high pressure to a material from many sides at once.