Mineralogy: discover the unique scientific value of diamonds that would have been sold in a jewelry store | Sciences

world of gems Tingting JuFrom Gemological Institute of America (GIA) In New York (USA), he was evaluating and verifying a diamond, about to be an integral part of another gem in a ring, when he realized its geological significance under the microscope. It was the second diamond Ringwood not discovered.

To learn about his discovery, Joe contacted Professor Fabrizio Nistola, researcher at the Department of Geosciences at the University of Padua (Italy). Diamond rarity IaB as it was named in the study published in magazine temper natureAnd the It consists of the minerals ferropericlase, ringwoodite and enstatite. “This is the first time this combination has occurred, confirming our experiments in the laboratory and giving us unprecedented knowledge of the composition and structure of one of the most inaccessible and remote places on Earth,” he explains enthusiastically. Nestola, co-author of the international study.

The gem is 1.5 cm tall, and in good condition, it came from Karoy mine in Botswana (Africa) Their analysis indicates that 660 kilometers underground there are minerals in contact with water. The work changes the known history of the Earth’s soil, as much more water is present in its geochemical composition than expected.

This discovery gives us unprecedented knowledge about the composition and structure of one of the most inaccessible and remote places on Earth

Fabrizio Nistola, researcher at the Department of Geosciences at the University of Padua (Italy)

Diamonds are a time machine (geological). Formed deep in the Earth millions of years ago, based on high pressure and temperatures, to be later expelled by subduction tectonic plates Across volcanoes s earthquakes. These minerals are one of the best ways to discover what’s going on thousands of kilometers deep inside the Earth, an environment that scientists don’t have direct access to.

The key piece of diamond in this latest study is ringwoodite, a magnesium silicate mineral, first discovered on Earth in 1969 in a meteorite hit Australia. Later, the first ground sample of This ore was mined in 2014. Sealed in “ultra-deep diamond”, Nestola confirms in Juína Mine in Brazil. The discovery confirmed theories about what the soil might have been at this depth. Between 400 and 600 kmwhich so far can only be analyzed by sediments expelled from geological disasters. Perhaps it arose from the depths embedded in it A volcanic rock called chimney kimberlite, Millions of years ago. “This was a great help,” Nistola notes, “because it is the largest well built by mankind Just Its length is 12 kilometers.

Ringwood is nothing more than a olivineone of the most common minerals in the Earth’s upper mantle, just below the crust, “to which great atmospheric pressure has been applied,” identifies the geologist Javier García Guinea, from the National Museum of Natural Sciences at CSIC. For him, not related to this research, the work is “ongoing”, but he understands that “this is a science, and it is being done step by step”.

The Gu team’s analysis of IaB placed it in the transition zone between Earth’s second and third layers, at a depth of 400 to 670 kilometers, where this diamond formed.at a pressure of 23.5 GPa and about 1650 °C. For reference, Nestola sarcastically compares: “The pressure that crushes the atoms of a metal until it becomes In diamonds it’s enormousone gigapa is equivalent to four mountain ledges on your head.”

The presence of H₂O in the lower mantle has consequences for the structure and evolution of the planet

Antonio García Casco, geologist at the Department of Mineralogy and Petrology at the University of Granada

The chemical composition of diamonds suggests that there is an ocean’s equivalent of water between the aquifers, “something not new and known for decades,” he explains. Antonio García Casco, geologist at the Department of Mineralogy and Petrology at the University of Granada. But at a depth of kilometers, it is not liquid water as we understand it on the surface. H₂O turns “liquid, half-liquid, half-gas” and sticks to metals that may contain up to 10% to 20% of its weight, the professor develops.

Casco considers the published work important because of the possibility of “inferring the presence of free H₂O in the lower mantle,” which has consequences for “the structure and evolution of the planet; for example, pregnancy mantle and the tectonic plateswhich is inevitable.” For the researcher, this study is an opportunity for mineralogists to witness metamorphisms that occur only “at depths that we will not be able to reach directly.”

preserved diamonds on the brink of death It ends with an engagement ring, “Freezing and capturing its environment, then hauling it, like a taxi, from the depths until it reaches the light,” makes Nestola. Moreover, for a geologist like him, the more material he absorbed, the more valuable it would be to study it. “Exactly the opposite for a jeweler,” laughs the co-author.

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