Analysis & grading

How GIA Identifies and Classifies Pearls



Although GIA is most recognised as the world’s foremost authority in diamond grading, it has been a leader in the identification and classification of natural and cultured pearls since 1949.
 
GIA has contributed to the revision of the FTC’s pearl guidelines for the jewellery industry and is responsible for working with major pearl companies globally to develop comprehensive standards for describing pearls. These standards are the GIA 7 Pearl Value Factors™: Size, Shape, Colour, Nacre, Lustre, Surface and Matching.

Inspection, care and handling procedures

GIA applies the same item identification and tracking procedures to all pearls as it does for coloured stones and diamonds. Each item is assigned a bar-coded label with a unique internal identification number that is used to track it throughout the process. And at every step, special inspection, care and handling procedures ensure that items are managed with the utmost care.

Weights and measures

This is the first stop for any item submitted for pearl services. Pearls are counted by hand and then weighed using an electronic micro-balance that captures the weight in grams (mounted or strung), carats (loose), or carats and grains (loose natural). Pearls are measured using special digital calipers.

Identification and classification

Items are then transferred to the Identification Inventory Control department for distribution to trained and experienced gemmologists for servicing. Once an item has been received by an initial gemmologist, its recorded weight and measurements are verified. The gemmologist identifies pearl types, molluscs and any detectable treatments using the standard gemmological testing and advanced testing equipment, including real-time X-radiography, UV-Vis reflectance spectroscopy and XRF. Real-time microradiography equipment is used to measure the nacre thickness of bead-cultured pearls if the nacre appears thin or when requested by the client. Loose pearls requiring more detailed analysis may be analysed using computed micro-tomography (μCT).
 
The gemmologist determines colour and classifies the other factors under a controlled viewing and lighting environment, using a comprehensive set of pearl masters. The pearl master sets include a hue circle and various colour grids to determine colour, and type-specific master sets of strands to classify lustre, surface and matching.
 
After that, the item is transferred to a second gemmologist, who independently repeats all the necessary observations and testing. Depending on its identity and nature, the item may be examined by additional gemmologists and research specialists.

Report processing and item return

Reports are generated after all results are finalised and services have been completed. All GIA Reports are examined and proofread to ensure quality before being sent to the client.
 
Lastly, the item is placed in its original container, joined by its report, and goes through final inspection and testing to ensure that the same submitted item is returned to the client.
 
Items are returned either in person through the Client Services department or via courier through the Transport Services department. All information recorded for an item remains stored in GIA’s permanent database for future reference.