Chinese Scientists Create Hexagonal Diamond—Harder Than Natural Diamond

Researchers in China have, for the first time, created samples of pure hexagonal diamond, a rare and theorized variant of diamond potentially harder than the cubic diamonds commonly found in jewelry and industrial applications. This achievement, detailed in a recent study published in Nature, addresses a long-standing challenge in materials science: producing and studying this elusive material, previously only observed in meteorites originating from shattered dwarf planets.

Natural, or cubic, diamond is renowned as the hardest naturally occurring material, forming the upper limit of the Mohs hardness scale—a system for measuring a mineral’s resistance to scratching. This scale relies on a cubic arrangement of carbon atoms. Hexagonal diamond, in contrast, arranges these same carbon atoms in a lattice resembling a honeycomb, a structure predicted to offer unique properties.

An Elusive Structure, Confirmed

The theoretical possibility of hexagonal diamond, also known as lonsdaleite, emerged in 1962 from research at the Pittsburg Coal Research Center. Scientists posited that carbon atoms could organize into a hexagonal lattice under specific conditions. The first documented discovery of hexagonal diamond occurred in 1967, sparking speculation about its potential hardness exceeding that of cubic diamond. Initial findings came from analyzing ureilite meteorites, formed within the mantles of destroyed dwarf planets. These meteorites, including Canyon Diablo (fragments from an Arizona crater) and Goalpara (found in India), contained small amounts of hexagonal diamond alongside the more common cubic form.

However, some scientists questioned these early detections, suggesting the observed structures might be flawed cubic diamond formations. Recent studies, including the new work from China, have strengthened the evidence for lonsdaleite’s existence, with a 2025 study successfully synthesizing small amounts of it in a laboratory setting.

A key obstacle to studying hexagonal diamond has been the difficulty in obtaining pure samples. Meteoritic lonsdaleite is typically intermixed with cubic diamond, graphite, and other minerals, hindering accurate property measurements. The Chinese team overcame this challenge by creating hexagonal diamond samples approximately 0.06 inches (1.5 millimeters) in diameter—large enough for detailed material property analysis.

Stiffness, Hardness, and Oxidation Resistance

The research team’s findings indicate that hexagonal diamond exhibits both greater stiffness and hardness compared to its cubic counterpart. Crucially, it also demonstrates significantly higher resistance to oxidation—meaning it can withstand higher temperatures without surface degradation caused by reacting with oxygen. This property is particularly valuable for applications like drilling and cutting tools, where heat generation is a concern.

According to Chong-Xin Shan, co-lead author of the Nature study and a physicist at Zhengzhou University, the research not only confirms the existence of hexagonal diamond but also establishes “a practical strategy for producing HD (hexagonal diamond) in bulk form.” This opens the door to larger-scale production and further scientific exploration.

The study’s methodology involved compressing highly organized graphite under extreme pressure—20 gigapascals (roughly 200,000 times Earth’s atmospheric pressure)—for ten hours, even as simultaneously applying temperatures ranging from 2,300 to 3,450 degrees Fahrenheit (1,300 to 1,900 degrees Celsius). Higher temperatures and pressures during this process led to a transformation of the hexagonal diamond back into the cubic form, highlighting the delicate balance required for its creation.

The implications of this breakthrough extend beyond materials science. The presence of hexagonal diamond in meteorites provides valuable insights into the formation and origins of these celestial bodies, furthering our understanding of the solar system.

The team’s work, as detailed in their published findings, provides “unambiguous confirmation” of hexagonal diamond’s identity through structural and spectroscopic analyses, supported by large-scale molecular dynamic simulations.

Potential applications for hexagonal diamond span a range of industries, including advanced cutting and polishing tools, heat dissipation systems for electronics, and quantum sensing technologies. The ability to produce this material in larger quantities could unlock innovations previously limited by the properties of cubic diamond.

Further research will likely focus on refining the synthesis process to improve yield and quality, as well as exploring the full range of hexagonal diamond’s potential applications. The findings will also prompt further investigation into the formation of lonsdaleite in natural settings, such as meteorite impacts and within the cores of dwarf planets, as described in a related article from Live Science.