Diamonds are a girl’s best friend, as the infamous song goes, but they’re also a scientist’s. There has been a long-standing belief that materials found deep below the Earth’s surface contain high levels of oxygen, but a new study on the world’s largest diamonds revealed something different.
Diamonds are mineral formed deep below the crust in the Earth’s mantle, brought up to the surface during volcanic eruptions. These rare and precious stones contain tiny flecks of metals and minerals inside them – “inclusions” that jewelers remove in order to present flawless, polished gems when they’re sold.
Scientists analyzed these inclusions in new research, in order to gather information on what is inside the Earth’s interior, Tech Times reports. Evan Smith and a team from the Gemological Institute of America took a closer look at the bits and pieces left over from cutting and polishing type IIa diamonds. These are the large, expensive type of diamonds under which famous stones such as the Cullinan, Constellation and Lesedi La Rona diamonds belong to.
The examination showed that the inclusions contained nickel, iron, carbon and sulfur enclosed in a layer of hydrogen and liquid methane.
This suggests that the diamonds formed under extreme pressure in patches of liquid metal that had little to no oxygen content.
These inclusions also suggested that some of the bigger diamonds are created at much deeper geological locations compared to smaller ones. For example, type IIa diamonds likely formed at depths from 224 to 466 miles in the convecting mantle, while other diamonds formed at around 93 to 124 miles in the lower portion of tectonic plates.
Researchers initially believed that the Earth’s mantle is composed of a uniform mix of oxygen-rich rocks, but this study suggests this theory may not be entirely correct. According to Smith, previous studies have predicted that the deep mantle contains small traces of metallic iron and limited oxygen levels. Their study supports this likelihood.
The study said, “We verify previous predictions that Earth has highly reducing deep mantle regions capable of precipitating a metallic iron phase that contains dissolved carbon and hydrogen.”
The analysis was published in the journal Science.
