Researchers have announced the first laboratory creation of pure hexagonal diamond, which, based on testing, exhibits slightly greater hardness than many natural diamonds. This achievement transforms a long-debated carbon structure into a measurable material and reshapes scientists’ understanding of diamond’s potential limits. The findings were published in the journal Nature.
Within a press compressed to 20 gigapascals, carbon formed a sample measuring 0.10 centimeters in thickness, which the researchers claim represents a pure new diamond structure. Following this pattern, Sigui Yang from Zhengzhou University (ZZU) linked the sample to a structure that has been the subject of longstanding debate.
Previous claims typically involved minuscule grains mixed with other carbon forms, making it difficult to prove the existence of a distinct material. A more refined approach altered this argument by providing researchers with sufficiently strong evidence for measurement, comparison, and verification.
As early as 1967, scientists reported finding lonsdaleite, a hexagonal form of diamond, in meteorites and fragments produced by meteorite impacts. Years later, in 2014, analysis suggested that these signals might originate from damaged ordinary diamonds rather than from a separate crystal.
This objection remained influential because the material was often found only as tiny, disordered fragments left behind after powerful impacts.
“These results resolve the long-standing debate over whether HD exists as a discrete carbon phase and provide new insights into the graphite-to-diamond phase transition, paving the way for future research and practical applications of HD in advanced technological fields,” wrote Yang.
The ZZU team started with graphite, a soft, layered form of carbon, because its stacked sheets can readily form a new structure. Pressure reached 20 gigapascals, while temperature rose from 1300 to 1900°C, causing these sheets to compress rather than shift sideways.
This direction was critical because bonds formed between the layers, transforming the slippery structure into a rigid three-dimensional network. Ultimately, the group discovered a fragment large enough for several direct experiments.
To test their claim, the team used X-ray diffraction—a method for mapping atomic positions—on the recovered crystal. In this experiment, X-rays bounce off atoms, and the resulting pattern reveals how the carbon atoms are arranged.
The results from studying the crystal matched the hexagonal structure, not the mixed patterns that had distorted earlier reports. Thanks to a better design, the evidence no longer relied on traces hidden within impact debris.
After confirming the structure, the group moved on to measuring Vickers hardness—a test that gauges resistance to indentation. Under a load of 9.8 newtons, the material reached approximately 114 gigapascals in one direction during repeated indentation tests.
Even so, the advantage over ordinary diamonds remained slight, making the result easier to trust. The most notable aspect was not a cartoonish leap in strength, but a confirmed edge in a disputed material.
Hardness alone would not make this material useful if high temperatures quickly degraded its crystal structure. Subsequent tests showed high thermal stability—the ability to maintain its structure when heated—compared to the original graphite.
This is important for cutting and drilling because the cutting edges of hot-rolled tools quickly lose their properties when the hard surface begins to break down. A material that retains hardness under loads and high temperatures becomes more suitable for use in machinery, electronics, and other fields requiring high strength.
Meteorite impacts can produce such diamond when carbon is suddenly compressed, heated, and rearranged under extreme stress. A 2022 study on meteorites suggested lonsdaleite might form before ordinary diamond during some powerful collisions.
These naturally occurring data help explain why this matters to researchers, since laboratory results can mirror the extreme process already happening in space. Still, matching nature is not the same as mastering production, and that gap determines whether this will be significant for industry.
In industry, diamonds are already used where tools need to cut, grind, or withstand intense friction without wearing out. A harder variant could last longer on surfaces, since fewer atomic bonds would break under pressure.
Researchers are also interested in electronics, because diamond efficiently conducts heat and resists damage in harsh environments. In real-world practical applications, it remains necessary to reliably produce larger pieces with lower costs and properties that engineers can reproduce.
One promising crystal does not guarantee complete success, as hardness can vary with direction, load, defects, and sample size. Other laboratories will now attempt to replicate the recipe, investigate larger samples, and test wear under real operating conditions.
They will also compare this material with the best artificially created diamonds, not just ordinary natural stones. The next round matters because an exceptionally hard material only earns trust after independent groups fail to disprove the claimed properties.
Chinese researchers did not merely create another tough laboratory crystal. They identified the clearest physical form of a disputed carbon structure. Whether it becomes a useful product or a scientific benchmark, the result will put future diamond research on a stronger foundation.
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