Scientists from U of A and UBC spot elusive mineral in diamond
Discovery offers insight into ‘the inner workings of the deepest parts of the Earth’
EDMONTON One of the most abundant minerals in the world — that had never before been seen on the Earth’s surface — has finally been eyed by scientists, thanks to one of the world’s most sought-after gems.
University of Alberta Department of Earth and Atmospheric Sciences professor Graham Pearson and colleagues from the University of British Columbia recently observed calcium silicate perovskite — one of five fundamental minerals that make up 99.99 per cent of the silicate mass of the Earth — in a diamond.
They posted their findings in the Nature journal Wednesday.
Scientists had long inferred the existence of calcium silicate perovskite, yet no one had ever been able to bring it to the surface because it is so unstable.
“A lot of science is inference. When you don’t know something is there, you find other evidence to infer that it is there,” Pearson said Wednesday. “In the end the inferences don’t prove what is there so there is nothing like having a real piece of it in your hand.”
As soon as the calcium silicate perovskite moves from where it’s happy at great depths inside the Earth, it wants to change instantly into some other crystalline form, Pearson said. “Diamonds are the only thing that stops that from happening,” he said.
High powered microscopy can be used in much of the research. However visual identification in a diamond is tough because it bends light — which is what makes them so beautiful — so it’s difficult for scientists to rely on what they are seeing because it is extremely distorted, he said. Instead scientists used spectroscopy where they used X-ray diffraction to show the arrangement of the atoms of the calcium silicate perovskite.
While the mineral is not economically valuable, its value to science is immeasurable.
“This mineral doesn’t have a use; its use is that it tells us a great deal of the inner workings of the deepest parts of the Earth,” he said.
Pearson said the calcium silicate perovskite they viewed probably grew at the same rate as the diamond and, as diamonds are the most incompressible of all natural minerals, it effectively created a protective barrier.
Subtle variations in its chemical composition tells scientists the mineral, which was brought up from a depth of about 800 km in a diamond mine in South Africa, actually started its life on the sea floor as a piece of oceanic crust, he said.
Over about a billion years, it was forced deeper into the Earth. “This gives us a picture of how oceanic plates, plate tectonics and how carbon is cycled into the Earth,” he said.