(IDEX Online) - Scientists have identified a mineral that has been seen before, trapped inside a "super-deep" diamond.The mineral, named davemaoite, originates in the Earth's lower mantle, at least 660km below the surface, according to the current edition of New Scientist magazine.The fact that tiny davemaoite crystals were found inside a diamond means it must have been formed at that depth. Most diamonds were formed at 120km to 250km underground.The super-deep diamond was recovered in 1987 at Orapa, in Botswana, the world's biggest open-cast mine, but was nobody had any idea how special it was.That all changed when Oliver Tschauner, a research professor in geoscience at the University of Nevada, Las Vegas, decided to X-ray the stone.He and his colleagues found fragments of calcium silicate, believed to exist in the lower mantle but had never actually seen before. In this rare instance the davemaoite was protected by the diamond and survived the high-pressure journey to the Earth's surface.The diamond is now at the Natural History Museum of Los Angeles County, in California, USA.Davemaoite was named in honor of deep-Earth scientist Ho-Kwang "Dave" Mao at the Carnegie Institution for Science, in Washington DC.Pic courtesy Natural History Museum of Los Angeles County.