In the last century, miners dug up a diamond in Botswana, which at first glance seemed to be nothing special. That didn't change either when the stone was sold to a Californian scientist in 1987, and eventually it ended up at the Natural History Museum of Los Angeles County. It was only when Oliver Tschauner from the University of Nevada in Las Vegas examined the diamond that the true value of the gemstone was recognized. So far, unique minerals have been enclosed in its interior, which originate deep from the Earth's mantle, as the geoscientist and his team report in "Science".
The Davemaoit called the Davemaoit, like the diamond surrounding it, come from the lower mantle of earth beyond 660 kilometers. In this way, they have developed at a greater depth than most other diamonds that come from areas between 100 and 250 kilometers below the earth's surface. Tschauner and Co had discovered the minerals during an X -ray examination of the gemstone, then cut it out with the help of a laser and examined mass spectrometric.
The crystals turned out to be a special form of calcium silicates: the calcium silicate perovskite. Theoretically, their existence in the lower coat has been predicted, but so far every proof has been missing. They only occur if they are pressed together under the extremely high pressure of around 40 gigapascal. In addition to uranium and thorium, the minerals had larger concentrations of potassium 40. The team also confirmed that the crystals in the earth's mantle can carry various radioactive elements that heat the interior of the earth due to their decay.
In addition, the analysis revealed lower concentrations of sodium and magnesium, which should not actually be present in the deeper mantle. They occur mainly in the earth's crust. The evidence suggests that, however, these elements can also enter the mantle through plate tectonics and be recycled.
The new mineral, named after the geoscientist Ho-K-Wang "Dave" Mao from Carnegie Institution for Science in Washington, D.C., only survived the trip to the surface thanks to the stabilizing cover from diamond. When the working group had worked out the Davemaoite from the diamonds, they only remained stable for a second. Then the mineral inflated and turned into a glass. In the lower coat, however, the Davemaoite are among the three most important minerals and could make up five to seven percent of the total material there. But it could be the only one of the three that uranium and thorium has in its structure. That also makes it unique at the moment.
