And fancy red is a very specific distinction. “It’s not reddish brown, it’s not reddish purple, it’s not reddish pink. It’s red.” Up close, the old-mine-cut diamond—shaped like a ...

The Smithsonian’s National Museum of Natural History has acquired the 2.33-carat “Winston Red Diamond,” one of the world’s largest fancy red diamonds. It will be unveiled to the public on ...