Oct 5th 2019ON SEPTEMBER 13TH a 16.78-carat yellow diamond, worth $2m, which was on display at the New York Stock Exchange, disappeared from view. Police were not, however, called to the scene. The disappearance was intentional. The diamond, part of an artwork called “The Redemption of Vanity”, had been coated in a “super-black” layer of carbon nanotubes which, by absorbing 99.995% of the visible spectrum, made the usually sparkling gemstone seem practically invisible inside its dark case.“The Redemption of Vanity” was a collaboration between Diemut Strebe, artist-in-residence at the Massachusetts Institute of Technology, and Brian Wardle, the institute’s professor of aeronautics and astronautics. Whatever moral message this artistic endeavour might or might not have been intended to convey, it was a stark demonstration of allotropy—the fact that a single element can come in many guises, depending on the arrangement of its atoms. For, like Dr Wardle’s nanotubes, diamonds are made of carbon. And that allotropic diversity is one of the reasons why carbon is such a useful material.Choose us for news analysis that respects your time and intelligenceSubscribe to The EconomistWe filter out the noise of the daily news cycle and analyse the trends that matterWe give you rigorous, deeply researched and fact-checked journalism. That’s why Americans named us their most trusted news source in 2017Available wherever you are—in print, digital and, uniquely, in audio, fully narrated by professional broadcastersThis website adheres to all nine of NewsGuard‘s standards of credibility and transparency.ORContinue reading this articleRegister with an email address