A diamond from 660 km deep reveals Earth's secrets: discover how this gem was extracted from the planet's depths (photos included).

From time to time, the Earth reveals hints about the mysterious processes taking place within its depths. This pertains to tiny chthonic diamonds that encapsulate fragments of a rare mineral. From these minuscule pieces, scientists can extract nuggets of information about what is truly happening in the Earth's interior, as reported by Science Alert.

An extraordinary diamond, formed approximately 660 kilometers beneath the planet's surface, has now come into the hands of scientists. It was discovered in a diamond mine in Botswana. The stone is riddled with inclusions containing traces of ringwoodite, ferropericlase, enstatite, and other materials that indicate their age. Furthermore, the presence of these materials suggests that the environment where the diamond formed—a boundary between the upper and lower mantle, also known as the 660-kilometer discontinuity—is rich in water.

According to the lead author of the study, mineral physicist Tingting Gu from the Gemological Institute of New York and Purdue University, the presence of ringwoodite alongside water-bearing phases indicates that a moist environment exists at this boundary.

It is no secret that a large portion of the Earth's surface is covered by oceans. However, scientists have previously demonstrated that there is a significantly larger reservoir of water hidden within our planet than what we observe on the surface. Meanwhile, the Earth's crust is a cracked and fragmented structure with individual tectonic plates that interact and slide beneath one another. In these subduction zones, water seeps deeper into the Earth's interior, reaching its lower mantle.

Over time, scientists believe that water returns to the surface through volcanic activity. This cycle of absorption and expulsion is known as the deep water cycle, distinct from the water cycle operating on the surface. Researchers note that understanding how this works and how much water is present is crucial for comprehending the geological activity of the Earth. The presence of water may also influence the explosiveness of volcanic eruptions and likely plays a role in seismic activity.

Unfortunately, current technologies do not allow humans to descend into the Earth's depths, so scientists must rely on the evidence provided by the planet itself. For instance, in the form of diamonds that form crystalline cells under extreme heat and pressure.

During the study, Gu and colleagues closely examined this unique diamond and discovered 12 mineral inclusions along with a milky-white cluster of inclusions. The team then utilized micro-Raman spectroscopy and X-ray diffraction to determine their nature. Among the inclusions, they found a collection of ringwoodite (a magnesium silicate) in contact with ferropericlase (magnesium/iron oxide) and enstatite (another magnesium silicate with a different composition).

At high pressures in the transition zone, ringwoodite breaks down into ferropericlase and another mineral—bridgmanite. At lower pressures closer to the planet's surface, bridgmanite transforms into enstatite. The presence of these minerals in the diamond tells a story of travel and indicates that the stone formed deep within the Earth's interior before returning to the crust.

The analysis also revealed that ringwoodite exhibited characteristics suggesting that it is hydrous in nature—that is, a mineral formed in the presence of water. Meanwhile, other minerals found in the diamond, such as brucite, are also hydrous. These clues indicate that the environment in which the diamond formed was moist.

It is worth noting that scientists have previously found evidence of water in the transition zone, but it was insufficient to assess the water reserves in the Earth's interior. Now, Gu's work with colleagues indicates that there is sloshing occurring deep within the Earth. Previous studies have shown that the Earth absorbs much more water than we previously thought. This may finally provide us with an answer to the question of where it is stored.