The normal place for diamonds to be born is 50 miles below Earth’s surface, in the hot mantle, where a pressure of 55,000 atmospheres and a temperature near 2,700 degrees Fahrenheit coaxes amorphous bunches of carbon atoms into organized crystals. But this past March, physicist Tyrone Daulton at Argonne National Laboratory in Illinois reported finding microscopic diamonds in a hunk of uranium-rich Russian coal that had never felt the mantle’s heat. Daulton explains that when uranium atoms fly apart inside a carbon-rich rock, they can slam into the carbon atoms (as illustrated at right) with enough energy to disrupt their chemical bonds. In the channel of destruction, the atoms will form new bonds, he says. Some of those are going to be diamond bonds.
But finding tiny diamonds in a large hunk of coal isn’t easy-- which is why the Russian scientists who first suggested they might be there, almost two decades ago, never succeeded. This time around, Daulton’s colleagues at the Russian Academy of Sciences dissolved the rock in a powerful acid that left only the most resilient minerals behind--thereby removing most of the haystack from the needle--and Daulton then used electron microscopy to hunt out the diamond crystals in the residue. Now that he knows how to get diamonds from coal, though, he isn’t about to get rich quick: it would take about a million trillion of his microdiamonds to make a single, commercial-size stone.