GIA (Gemological Institute of America) has announced that it is suspending its diamond sealing services. The suspension is effective immediately and comes following the discovery that “a small number” of GIA sealing packets that had been compromised by third parties after the sealing packets left GIA. 
The Institute said that in these cases, the original diamonds had been replaced with HPHT (high-pressure, high-temperature) treated natural diamonds. 
The replacement diamonds superficially matched the GIA report information for the original diamonds, including information on the sealing packet data label.
GIA said that anyone who has concerns about a GIA-sealed diamond can submit the unopened packet to any GIA laboratory for verification services. If GIA concludes the diamond in the sealing packet is the diamond described in the original report, the Institute will issue a verification letter confirming the diamond matches the original report. If this is not the case, the Institute will issue a new report with the correct results. 
The Institute will provide this verification service free-of-charge for diamonds received in a sealed packet. All sealed diamonds submitted will be returned unsealed.
Source: DCLA