Yet another research group says they have a faster, cheaper method to manufacture large synthetic diamonds.

Researchers at the Geophysical Laboratory at the Carnegie Institution of Washington say they have come up with a “breakthrough” variation on chemical vapor deposition, the method used by Boston’s Apollo Diamond Inc. Apollo says it can grow large colorless stones but cannot manufacture them consistently.

Dr. Russell Hemley, a scientist involved in the project, says his new method could lead to mass production. “We can make a nice 2.5 mm high gem in one day,” he says. He also says there may be virtually no limit to size: “We believe that 300-carat diamonds are eventually possible with this approach.”

Still, he has no plans to market it for jewelry applications: “We are an academic group and our interest is primarily scientific and technological applications—which generally requires higher-quality material than is needed for jewelry,” he says.

Last month, scientists at the University of Alabama at Birmingham announced a microwave-based technology that they said could also lead to mass-produced stones. (See “University Claims ‘Better, Faster’ Synthetic Diamonds,” JCK, June 2005, p. 51.)