South Korean researchers have developed a new technique for creating synthetic diamonds — and they think they’ve only scratched the surface of its potential. Synthetic diamonds: Aside from jewelry, diamonds are used in drilling, manufacturing, healthcare, quantum computing, and more. The cost and uncertainty of finding the right kind of diamonds in nature inspired scientists to see if they could make them in the lab. In the 1950s, a team at General Electric pulled it off using a process called “high-pressure high-temperature” (HPHT), which mimics the conditions that create diamonds in nature. This process is still used to make 99%...