Measuring Carat Weight

Carat Weight and Measurements
Before a diamond enters the GIA Laboratory for grading, it is labeled with a unique internal identification number used to distinguish and track it through processing. At this point, client information is removed from the diamond packaging, and the diamond proceeds to its first stop –the Weights and Measures Department.

Here, the diamond is weighed using a very accurate electronic micro-balance that captures the weight to the fifth decimal place. An optical measuring device is used to determine the diamond’s proportions, measurements and facet angles. This data is uploaded into Horizon, GIA’s operations and information management system.

After weighing and measuring, the diamond is placed into a transparent storage case that is labeled with its internal ID number, weight, measurements and requested services. When applicable, the diamond’s unique GIA Report Number is also assigned at this time.

Screening and Advanced Testing for Diamond Identification and Color Origin
Next, the diamond undergoes a technical screening process to determine if it is potentially synthetic, high pressure/high temperature (HPHT) processed, or a diamond simulant. If further screening is required, advanced testing is performed by the Identification Services department using state-of-the-art technology such as Fourier transform infrared spectrometry (FTIR) and Raman spectroscopy to determine the item’s identity and color origin. These tests are also performed on all items submitted for colored diamond services. Bottom line, this is where it is natural and of natural color or evidence to the contrary is revealed.

Inscription
At the client's request, a diamond may be microscopically inscribed on its girdle with its unique GIA Report Number (referred to as the GIA Inscription Registry), a personal message, or other text, symbols or logos. An inscription allows for easy identification of a diamond, a way to personalize the diamond, or serves as a form of branding for the diamond manufacturer or retailer.