Diamonds are not necessarily colorless. It can also be blue, yellow, green, or even pink. But why do these gems come in a variety of shades?
On its base, diamonds are made of a single element, carbon. “It’s just pure carbon,” said Luc Doucet, a senior geology researcher at Curtin University in Australia. They are usually deep below the surface of the Earth, over 100 miles (161 kilometers) in the planet’s mantle. Here, the pressure and temperature are extreme enough to allow carbon atoms to bond in a tight lattice.
Once formed, the diamond must rise very quickly for the lattice to remain intact. This usually occurs when a volcanic eruption drains rocks from its depth. If the diamond stays deep, it can melt or transform into graphite for millions of years.
You might like it
Gabriella Farfan, curator of Coraline Whitney, gems and minerals at the Smithsonian National Museum of Natural History, said:
Most of the diamonds are colorless. However, there are several ways that a regular diamond can turn into a “fantastic coloured diamond,” Farfan said.
First, like all minerals, diamonds can obtain impurities when they are formed. These defects are non-carbon elements that are integrated into the structure of the gem. However, carbon molecules are very small and packed so tightly that there are very few elements introduced into diamonds. “There aren’t many substitutes,” Farfan said.
Related: Which is more unusual: Diamond or emerald?
However, there are a few exceptions. Nitrogen, the carbon neighbor of the periodic table, can sneak into the diamond lattice to create yellow or orange diamonds. Another element with a small atomic radius, boron can create impressive blue diamonds such as the famous Hope Diamond.
Radioactive radiation can also turn diamonds green. This can occur when there is uranium in adjacent rocks near the gem. Uranium can “eject atoms to create vacant spaces” into the diamond structure, Farfan said.
Diamonds can also obtain color through structural transformation. This is how pink and red diamonds are formed. These stones receive these shades because the carbon lattice is distorted when they are deep within the planet.
Diamonds must be crushed in the right way to take on the pink or bright red shade. “It’s like Goldilocks,” Dessett said. If the diamond is under too much pressure it can turn brown. If it’s not under sufficient pressure, it remains colorless. “There are a lot of brown diamonds, very few pink diamonds,” Doucet said.
Interestingly, how pink and red diamonds form allows scientists to analyze these gems and understand exactly where, when and where they occur in the Earth’s crust. Regional geological processes leave a signature of the diamond transformation. “This way, pink [and red] Diamonds are the only diamonds that could bring them back to a geographical region,” Farfan said.
Doucet, for example, was studying pink diamonds from the Argyle Mine in Western Australia, one of the world’s largest diamond mines. Looking at the structure of the gem, he and his colleagues identified that stones were created during the Earth’s first supercontinent division 1.3 billion years ago. The results were published in a 2023 study in the journal Nature Communications.
Farfan pointed out that the Winston diamond, which was recently exhibited at the Smithsonian National Museum of Natural History, is bright red. Based on the analysis published in the journal Gems & Gemology, it could have come from somewhere in Venezuela or Brazil.
Studying these flashy coloured diamonds can be a useful tool for science as well. They can help researchers understand what is happening within the planet, and how the carbon cycle has changed throughout the Earth’s history, Doucet said.
These diamonds are special. Because “the Earth produced them under these unique circumstances,” Farfan said. “It’s just a miracle that it exists in the first place.”
Source link
