Why do diamonds come in different colors?
Diamonds are not always colorless; They can also be blue, yellow, green and even pink. But what makes these jewelry come by various shades?
At their base, diamonds are made of a single element: carbon. “It’s just pure carbon,” forged treasures under very high pressures, said Luc DoucetMain researcher in geology at Curtin University in Australia. They generally form deeply below the surface of the earth, more than 100 miles (161 kilometers) in the planet’s coat. Here, the pressure and temperature are extreme enough for carbon atoms to bind together in a tight network.
After the formation, diamonds must raise the surface very quickly so that their network remains intact. This generally occurs when volcanic eruptions eject the rocks of the depths. If a diamond remains in the depths, it can melt or turn into graphite over millions of years.
“We are in fact very lucky that we can even find them, because they must then be expelled from the deep earth,” said Gabriela FarfanCoraryn Whitney Conservative of jewels and minerals at the Smithsonian National Museum of Natural History.
The majority of diamonds are colorless. But there are a few ways whose normal diamonds can turn into “fancy diamonds,” said Farfan.
First of all, like all minerals, diamonds can obtain impurities when they form. These defects are elements other than carbon which integrate into the structure of the gem. But because carbon molecules are so small and very closely packed, very few elements can be introduced into diamonds. “There are not many elements that can be replaced,” said Farfan.
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However, there are some exceptions. Nitrogen, neighboring carbon on the periodic tableCan sneak into the diamond trellis, make yellow or orange diamonds. The boron, another element with a small atomic radius, can make striking blue diamonds, like the famous Diamond of Hope.
Radioactive radiation can also make diamonds green. This can happen if neighboring rocks near gems have uranium, which can “expel atoms to create vacant positions” in the diamond structure, said Farfan.
Diamonds can also obtain their color thanks to structural deformations. This is how pink and red diamonds are formed. These stones get these colors because their carbon networks deform when they are deep inside the planet.
A diamond should be crushed in the right way to take a pink or bright red shade. “It’s a bit like Goldilocks,” said Doucet. If a diamond is put under too much pressure, it can become brown; If it is not under enough pressure, it remains colorless. “There are a lot of brown diamonds, and very, very few pink diamonds,” noted Doucet.
Interestingly, because of the way in which pink and red diamonds are formed, scientists can analyze these jewels and understand exactly where and when in the crust of the earth, they come. The geological processes of an area leave a signature in the deformations of a diamond. “So, in this way, pink [and red] Diamonds are the only ones you could potentially try to trace to a geographic region, “said Farfan.
For example, Doucet studied pink diamonds of the Argyle mine in Western Australia, one of the largest diamond mines in the world. Looking at the structure of the Gems, he and his colleagues identified that the stones were made during the rupture of the first supercontinent of the earth 1.3 billion years ago. The results were published in a study in 2023 in the journal Nature communications.
Farfan stressed that the Winston Diamond, recently exhibited at the Smithsonian National Museum of Natural History, is bright red. And depending on An analysis published in the journal Gems & GemologyHe probably came somewhere in Venezuela or Brazil.
The study of these fancy diamonds can also be a useful tool for science. They can help researchers understand what was going on inside the earth and how carbon cycles moved throughout the history of the planet, Doucet said.
These diamonds are special because “the earth produced them in such unique circumstances,” said Farfan. “It’s just a miracle that there is even first.”
