South African diamond provides new clues on Earth's internal processes


While rare to human eyes, calcium silicate perovskite may be shockingly ordinary deep inside the Earth - in fact, it's thought to be the fourth most abundant mineral inside the planet, especially prevalent in slabs of oceanic crust that have plunged into the planet's mantle at tectonic boundaries.

Oliver Tschauner, a professor of geoscience at the University of Nevada, Las Vegas, explained that there are actually several known phases of water ice that form under different pressure and temperature conditions. As the diamond was pushed to the surface, it would have cooled while still under pressure, and the ice VII formed within. Other known sites of its existence are Jupiter's moon Europa, and Saturn's moons Titan and Enceladus.

While we now know that we can find ice-VII on Earth, it's by no means easy to find.

Pearson explained that the diamonds from the mine are among not only the most commercially valuable in the world, but they are also the most scientifically valuable, providing insight into the deepest parts of Earth's core. However, the authors of the study recently discovered that diamonds are capable of trapping small bubbles of pressurized water when they form deep in the mantle. It is about 2,900 kilometers thick and comprises 84 percent of the Earth's total composition.

In the new study, Pearson and his colleagues analyzed a tiny diamond (roughly 3 millimeters across) excavated from Cullinan less than 1 km (0.6 miles) below the Earth's surface.

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. As you'll recall, the mantle is too warm for ice-VII to exist.

Although the study provided the direct evidence of unbonded water at extreme depths, the researchers were not able to determine how large these water pockets are and how common they are. They crack and whatever inclusions they had in them are lost. This water was encapsulated within the diamond, and would have remained liquid due to the intense heat down there. What does allow ice-VII to form naturally, however, is diamonds.

An global team of researchers have discovered high-pressure ice crystals embedded inside diamonds, technology, science and science fiction website Gizmodo reported. These ice VII samples are the first time this form of crystalized water has been seen in nature and led the International Mineralogical Association to declare ice VII as a new type of mineral. Ice-VII is unique in that it remains fairly stable even as the pressure continues to increase.

"Water in diamonds is not unknown, but finding this very high pressure form of water ice intact, that was really fortuitous", he said.