In the last century, miners in Botswana unearthed a diamond that, at first glance, seemed nothing special. This did not change when the stone was sold to a California scientist in 1987, and it eventually ended up at the Natural History Museum in Los Angeles County. It was only when Oliver Tschuner of the University of Nevada in Las Vegas examined the diamond that the true value of the gem was recognized. Its interior contains so far unique minerals that come deep in the Earth’s mantle, As the geologist and his team report in “Science”,
Like the diamonds around them, the sprinkles called Dawemaot come from the lower reaches from a depth of 660 kilometers. This means that they evolved at a greater depth than most other diamonds, coming from regions 100 to 250 kilometers below Earth’s surface. Tschauner and Co discovered the minerals during X-ray examination of the gemstone, then laser-cut them and examined them by mass spectrometry.
Crystals turned out to be a special form of calcium silicate: calcium silicate perovskite. Its presence in the lower mantle has been speculated theoretically, but so far no evidence has been found. They only occur when they are compressed under extremely high pressures of about 40 gigapascals. In addition to uranium and thorium, the minerals contained high concentrations of potassium-40. The team also confirmed that crystals in Earth’s mantle may contain various radioactive elements that heat Earth’s interior through their decay.
In addition, the analysis revealed low concentrations of sodium and magnesium, which should not actually be present in the deep mantle. They are mainly found in the earth’s crust. Evidence indicates that these elements also enter the mantle through plate tectonics and may be recycled.
