AGS Laboratories has suspended all diamond grading for a month, because of coronavirus.
The facility in Las Vegas, Nevada, has been forced to close in a bid by the state governor to halt the spread of Covid-19.
All "non-essential businesses" are included in the closure order, which became effective yesterday and which will remain in place for at least a month.
The lab, founded in 1996, provides expert, third-party evaluation of a diamond's quality characteristics.
The American Gem Society (AGS) headquarters will still function during normal office hours, staffed remotely.
Eralier this week AGS canceled its Conclave, an annual education, social and networking event for jewelry traders in April, also because of coronavirus.
"Because of the nature of the work we do at AGS, our team can adapt their work to a virtual office," said Katherine Bodoh, CEO of American Gem Society and AGS Laboratories.
"However, the same is not true for AGS Laboratories. Therefore, I regret to inform you that effective today at noon, Pacific Time, AGS Laboratories will be temporarily closed for at least 30 days, until the state-mandated closure ends.
"Please continue to take precautions in your business, with your team, and your loved ones. We want to hear from you, as well, and please do not hesitate to reach out to us."