Rare half-pink rough diamond with ‘astounding’ weight of 37.4 carats discovered in Botswana
Miners have discovered a rare two-tone natural diamond in Botswana – and experts say it likely formed in two stages.
The diamond is half pink, half colorless. It measures approximately 1 by 0.63 by 0.57 inches (24.3 by 16 by 14.5 millimeters) and weighs a “staggering” 37.41 carats (0.25 ounces or 7.5 grams), according to the Gemological Institute of America (GIA), a nonprofit research center based in Carlsbad, California.
The pink half probably formed first, but based on what scientists know about colored diamonds, there’s a good chance it wasn’t always this pink. Sally Eaton-Magañalead diamond identification officer at GIA, said in an emailed statement to Live Science. “The pink section was probably initially colorless and then plastically deformed, perhaps by a mountain-building event millions of years ago, giving it its pink color, with the colorless section forming later,” she said.
Pink diamonds are incredibly rare, and it’s still unclear exactly how they form. The diamonds come from more than 100 miles (160 kilometers) beneath the Earth’s surface, inside a planetary layer called the mantle. Extremely high temperatures and pressures bind carbon atoms into a tight network, and this structure can quickly rise to the surface through volcanism, giving us rough diamonds.
Diamonds can gain color from impurities that remain trapped inside the lattice, but this is very rare because few elements are small enough to penetrate the mineral structure. Another way diamonds can become tinted – usually green – is through radiation, if nearby rocks contain elements such as uranium that can “steal” carbon atoms and create gaps in the mineral structure.
But pink diamonds are the product of structural deformation, meaning their lattice structure has been folded or compressed by geological processes. Temperature and pressure conditions must be ideal for diamonds to turn pink, as too much deformation causes gemstones to turn brown.
“It’s a bit like Goldilocks” Luc Doucetsenior research geologist at Curtin University in Australia, previously told Live Science. “There are a lot of brown diamonds and very, very few pink diamonds.”
For a diamond to have two distinct color zones, it must have formed in two phases, according to the GIA. First, the half-assembled and distorted pink; Then the colorless half has germinated and its network is not affected by temperature and pressure.
This new diamond is not the first natural pink and colorless diamond ever discovered. However, GIA experts said similar diamonds they examined were much smaller, weighing no more than 2 carats (0.014 ounces or 0.4 g).
The new discovery comes from the Karowe mine in Botswana, which has previously produced other spectacular diamonds. For example, this is where the second largest rough diamond ever recovered – a giant 2,488-carat (1.1 pound or 0.5 kilogram) gemstone nicknamed the “Motswedi” diamond – and the 62-carat (0.44 ounce or 12.4 g) diamond Pink diamond “Boitumelo” were discovered, the GIA said.
