Diamond hauled from deep inside Earth holds neverbefore-seen mineral
Within a diamond hauled from deep beneath Earth’s surface, scientists have discovered the first example of a never- before-seen mineral. Named davemaoite after prominent geophysicist Ho-kwang (Dave) Mao, the mineral is the first example of a high-pressure calcium silicate perovskite (CaSiO3) found on Earth. Another form of CaSiO3, known as wollastonite, is commonly found across the globe, but davemaoite has a crystalline structure that forms only under high pressures and temperatures in Earth’s mantle, the mainly solid layer of Earth trapped between the outer core and the crust.
Davemaoite has long been expected to be an abundant and geochemically important mineral in Earth’s mantle. But scientists have never found any direct evidence of it because it breaks down into other minerals when it moves towards the surface and pressure decreases. Analysis of a diamond from Botswana, which formed in the mantle around 660 kilometres below Earth’s surface, has revealed a sample of intact davemaoite trapped inside. The International Mineralogical Association has confirmed davemaoite as a new mineral. “The discovery of davemaoite came as a surprise,”said Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas.
Tschauner and his colleagues uncovered the davemaoite sample with a technique known as synchrotron X-ray diffraction, which focuses a high-energy beam of X-rays on certain spots within the diamond with microscopic precision. By measuring the angle and intensity of the returning light, researchers can decipher what’s inside, Tschauner said. The sample of davemaoite within the diamond was just a few micrometres in size, so less powerful sampling techniques would have missed it, he added. Davemaoite is believed to play an important geochemical role in Earth’s mantle. Scientists theorise that the mineral may also contain other trace elements, including uranium and thorium, which release heat via radioactive decay. Therefore davemaoite may help to generate a substantial amount of heat in the mantle.