A new study, published in Nature magazine and quoted by multiple news sources, has revealed that blue diamonds – which account for less than 0.02% of all diamonds mined – are formed deeper in the Earth’s crust than other types of diamonds. The most famous blue diamond is the Hope diamond, discovered in India in the 17th century.
A research team from the Gemological Institute of America (GIA) applied Raman spectroscopy on 46 type IIb blue diamonds, and found that these stones were formed as deep as 750 kilometers below ground. Most diamonds are formed less than 200 kilometers below ground. This area in Earth is located between the upper and lower mantles.
Evan Smith, head of the research team, said that “These so-called type IIb diamonds are tremendously valuable, making them hard to get access to for scientific research purposes”. Their inner impurities give them their blue color, and are essentially microscopic flecks of boron. While boron is usually found near the planet’s surface, the researchers think that these diamonds’ boron may have come from the ocean floor. These ocean floors were then pushed down into the Earth’s mantle and under extreme pressure, the boron found its way into the diamonds.
