Gemologist Tingting Gu was working on the Gemological Institute of America (GIA) in New York when a diamond got here to her for evaluation and appraisal. It was to be set in a hoop and bought in a jewellery retailer earlier than she realized the geological significance of the gem underneath her microscope. It was the second ringwoodite diamond ever found.

To validate her discover, Gu contacted Fabrizio Nestola, a professor with the Division of Geosciences at Italy’s College of Padua. The IaB-type diamond may be very uncommon as a result of it reveals a mineral accumulation of ringwoodite with ferropericlase and enstatite. “That is the primary time that this mix has occurred, which validates our laboratory experiments and supplies us with distinctive new information in regards to the composition and construction of one in all Earth’s most inaccessible and distant locations,” mentioned Nestola, co-author of the examine printed in Nature.

The 1.5 cm diamond comes from the Karowe mine in Botswana in southern Africa. A chemical evaluation of the gem signifies that it originated 410 miles (660 kilometers) beneath the Earth’s mantle, the place it got here involved with water. This discovering modifications scientists’ present understanding of the Earth’s subsoil in that water is now believed to be far more prevalent at that depth than beforehand thought.

Diamonds are geological time machines. Excessive strain and temperatures shaped diamonds in Earth’s depths hundreds of thousands of years in the past. Volcanic eruptions, earthquakes and tectonic plate actions then introduced them as much as the Earth’s crust. Diamonds are among the best sources of details about what is going on deep contained in the Earth, an surroundings to which scientists haven’t any direct entry.

The diamond that got here into Tingting Gu’s arms accommodates ringwoodite, which is a magnesium silicate mineral first found in 1969 in a meteorite that struck Australia. The first terrestrial ringwoodite pattern was excavated in 2014 from the Juína mine in Brazil, sealed inside a “super-deep” diamond, in line with Nestola. The invention confirmed scientific theories in regards to the Earth’s mantle, which may solely be studied through the deposits expelled by geological cataclysms. It more than likely emerged hundreds of thousands of years in the past from the depths by means of a “chimney” of kimberlite volcanic rock. “This was very useful,” says Nestola, “as a result of the longest artifical shaft ever constructed solely goes 7.5 miles deep.”

Ringwoodite is nothing greater than an olivine, one of the widespread minerals within the Earth’s higher mantle, just under the crust, “… to which nice atmospheric strain has been utilized,” says geologist Javier García Guinea, of Spain’s Nationwide Museum of Pure Sciences. García Guinea, who was not concerned within the uncommon discovery, says the examine is “continuist” in nature, however acknowledges that “that is science, which is finished step-by-step.”

The evaluation of the IaB-type diamond signifies that it comes from a transition zone between the second and third layers of the Earth, at a depth of between 250 and 420 miles. The diamond was shaped at a strain of 23.5 GPa (gigapascals), and a temperature of about 3,000ºF (1,650ºC). To assist us comprehend these details, Nestola explains: “The strain that crushes the atoms of the mineral right into a diamond is immense – a single gigapascal is equal to 4 Mount Everests on high of your head.”

The presence of H₂O within the Earth’s decrease mantle has implications for the construction and evolution of the planet

Geologist Antonio García Casco (Division of Mineralogy and Petrology, College of Granada, Spain).

The chemical composition of the IaB-type diamond means that there are oceans of water between the Earth’s substrata, “which isn’t new data – this has been identified for many years,” says geologist Antonio García Casco, from the Division of Mineralogy and Petrology at Spain’s College of Granada. However at these excessive depths, water just isn’t the liquid we see on the floor. “It [H₂O] is remodeled right into a fluid that’s half-liquid and half-gas. It adheres to minerals and might comprise between 10-20% of their weight,” says García Casco.

García Casco says the examine in regards to the IaB-type diamond is important as a result of it leads us to “infer the presence of free-flowing H₂O within the decrease mantle,” which has implications for “the construction and evolution of the planet. For instance, implications for mantle convection and plate tectonics, which completely change the planet.” For García Casco, this examine is a chance for mineralogists to look at transformation processes that solely happen “at depths that will likely be without end inaccessible.”

The diamond, saved within the nick of time from ending up in an engagement ring, “freezes and captures its surroundings, after which ferries it up from the depths till it reaches the sunshine of day,” says Nestola. For geologists like him, the extra materials a gem absorbs, the extra helpful it’s to science. “Simply the other for a jeweler,” he laughs.