De Beers is once again testing the “Forevermark,” its diamond-shaped logo inscription meant to reassure consumers about the diamonds they buy. The test will take place in Hong Kong with a limited number of retailers and sightholders.

The DTC says the mark will “guarantee your diamond is a genuine natural diamond [that] has not been altered or treated by any artificial means,” says spokeswoman Lynette Hori. But the mark also has raised controversy. Some worry that if the DTC tells consumers that diamonds with the Forevermark are okay, they’ll get the impression that others are not. The Diamond Manufacturers and Importers Association recently complained that the Forevermark’s “planned use will be permitted only to firms within its own carefully restricted network.”

Hori says the mark is just meant to improve consumer confidence.

“The DTC Forevermark consists of a trail of assurance from the DTC to the consumer,” Hori says. “It will also provide detailed learning about the implementation of the process through the pipeline.”

Each diamond will have the Forevermark logo inscribed on its table, along with a serial number. The mark is invisible to the naked eye, barely visible under a 10-power loupe, and can be seen only by using a special Forevermark viewer. The DTC says that a key benefit of the proprietary table-marking process is that it can be seen irrespective of the stone’s setting, whereas a girdle mark can be obscured by certain mounting methods.