A team of Chinese researchers has reportedly come up with a way to create small diamonds from carbon dioxide, according to a report in New Scientist. The team’s method could be cheaper and less expensive than current methods of creating synthetics, since the diamonds are created at a lower temperature.

At first, the group was able to produce diamonds only one millimeter in size—too small for gems. But now they say they can grow small gems that they call transparent and colorless.

Not everyone is impressed. One researcher quoted in New Scientist doesn’t think the new process will replace current methods of creating synthetics, noting the stones produced so far have been “gritty.”