The diamond laboratory of the Gemological Institute of America (GIA) has dropped a number of clients that sent in High Temperature, High Pressure (HPHT)-treated diamonds without disclosing the treatment, Senior Vice President Tom Moses informed Jewelers' Circular Keystone.

GIA policy stipulates that all diamond treatments must be noted in writing when a stone is submitted to the lab for grading.

Moses, while he did not reveal the names of the diamond companies who had violated the GIA's code of conduct, explained that the GIA was taking steps to "protect the industry" and said that they would be reported to diamond trade organizations such as the World Federation of Diamond Bourses.

In December, the GIA lab said that it was seeing more HPHT-treated diamonds, not all of which were properly disclosed as such.