Jennifer Lopez is engaged to Ben Affleck again, but to a mineralogist, the bigger news might be the massive green diamond atop her ring. At 8.5 carats, according to Page Six, it just might unseat the Dresden Green as the best-known diamond of its kind (a whopping 41 carats, but connected to zero rekindled 2000s romances at this time).
Diamonds are made of carbon atoms arranged in a rigid lattice-like structure that forms in the extreme conditions of the Earth’s mantle. The most common diamond colors you’ll see are clear, black, and brown. Other colors are much rarer—as flawless as green or pink stones might look, they get their hue from specific imperfections in the diamond’s structure.
In a clear diamond, every color gets reflected. But in the case of a green diamond, there are enough errors of a specific type that it reflects a green color. The imperfections in green diamonds are most commonly caused from radiation damage. Radiation from nearby uranium or thorium ore can hit a diamond’s carbon structure and warp it ever so slightly, which causes light to bounce off of it differently. The distinctive color could also come from chemical impurities: If an element that’s not carbon gets enmeshed in the diamond structure, like nitrogen, hydrogen, nickel, or sulfur, that could also alter the structure just enough to create a similar light-bouncing effect that produces a green color.
Though imperfections in a lattice structure aren’t that rare on their own, it’s a “constellation” of imperfections that can give a diamond a particular hue. “If there’s radiation damage, and it only damages one single site in a two carat diamond, you’re probably not going to see a green color,” says Shaunna Morrison, a mineralogist at the Carnegie Institution for Science. “You need enough site damage that you’re actually seeing a little tiny bit of change in the crystal structure in order to make that happen.” Essentially, you need the carbon atoms to form in the right configuration with just enough radiation damage in just enough spots in the diamond to produce green. As Morrison put it, “the perfect storm of geology that it takes to create these is rare, essentially.”
The diamond that Affleck gave J.Lo for their first swing at an engagement was actually a rarer color than green: pink. Pink and red (which the Gemological Institute of America classifies as one category) are considered to be the rarest of colorful diamonds. These are formed from similar deformations in the carbon structure called “plastic deformations.”) In the rarity scale though, green is definitely up there, along with blue (caused by boron impurities) and yellow (caused by nitrogen impurities). And lest we forget the size of J. Lo’s rock—while 8.5 carats might not be as impressive for a black or white diamond, it is very impressive for green.
“If you have a perfect diamond, like yeah, it’s gorgeous, that’s cool,” says Morrison. “But the imperfections are really what make it kind of interesting and rare.” Two titans of celebrity engaged again? Dare we say a relationship forged under intense pressure, and with very specific imperfections, makes for dazzling gossip.