GIA 7 Pearl Value Factors

Pearls of Wisdom - 11 Interesting facts about pearls

Pearls And The GIA 7 Pearl Value Factors


The GIA uses a comprehensive standard it developed over a 60-year period of ground-breaking research on pearls, called The GIA 7 Pearl Value Factors™ (Size, Shape, Color, Luster, Surface, Nacre, and Matching).

The GIA 7 Pearl Value Factors™ provide a systematic way to evaluate pearls of all types, and to describe their appearance and quality in a way everyone can understand.

Queen Of Gems

Treasures from the earth’s rivers, lakes, seas, and oceans, pearls have always embodied the power and life-sustaining nature of water.
The natural pearl is quite likely the earliest gem used for adornment. Our ancestors foraged seashores and riverbeds collecting mother-of-pearl shells for ceremony and exchange. When a rare pearl was found, it became a sacred possession.

Ancient Persians associated pearls with tears of the gods. Ancient Greeks believed they were created by moonlight on the water. To ancient Chinese, they guaranteed protection from fire. For Europeans, pearls symbolized modesty, chastity, and purity, and are still considered traditional gems for brides.
While natural pearls remain very rare, pearls today are no longer the sole property of royalty and the wealthy. Thanks to advances in modern culturing techniques, pearls are one of the most accessible gems worldwide.

What Is A Pearl?

Pearls are gems that form inside a living seawater or freshwater mollusk. They come in a dizzying array of sizes, colors, and shapes. This is due to the unique conditions under which pearls form, with mollusk species, environmental conditions, and often human ingenuity all playing a part in creating incredible diversity.

Natural Pearls

When the mantle of a mollusk is naturally irritated by what may be an organism of microbe size, a “pearl sac” forms and isolates the irritant within the mantle. The mollusk secretes calcium carbonate, often in the form of nacre, to cover the irritant. As the mollusk deposits further layers, the pearl gradually grows in size. Natural pearls occur randomly and most are usually irregularly shaped. Large round natural mantle pearls are especially rare—and prized.

Bead Cultured And Non-Bead Cultured Pearls

When a pearl forms with human assistance, the result is a cultured pearl. Technicians instigate formation by implanting a bead and/or piece of mantle tissue into a mollusk. The implanted tissue deposits layers of nacre over the bead (bead cultured), or over secreted organic material (non-bead cultured) and over time a miraculous pearl is born.

Pearl Treatments

Human intervention may occur or continue after harvest in an effort to improve a pearl’s color, shape, surface appearance, weight, and durability. Processes may include bleaching, heating, dyeing, irradiation, and coating to enhance color; peeling to improve shape and/or surface appearance; or filling and impregnation to increase weight or enhance durability.

What Is A Keshi Cultured Pearl?

“Keshi” is an old trade term for a small natural seed pearl. Today, the term is often used to describe a non-bead cultured pearl of any size that forms in marine pearl-oysters or freshwater mussels as a by-product of the culturing process.

What Is A Blister Pearl?

A mollusk may initially produce a pearl in the mantle that eventually adheres to the inside of the shell and forms a “blister pearl” rather than forming in the mantle. Natural “blisters” occur around a variety of irritants that become trapped between the mantle and the shell.

GIA‘s 7 Pearl Value Factors™

Size – Stated in millimeters, to two decimal places.
Shape – Described as round, near-round, oval, button, drop, semi-baroque or baroque. Pearls not falling into these groupings are described as they appear.
Color – A combination of the pearl’s dominant bodycolor, overtone, and orient.

  • Bodycolor takes into account hue, tone, and saturation
  • Overtone is a noticeable translucent color that appears to overlie the bodycolor
  • Orient is a mixture of colors shimmering just below the pearl’s surface

Luster – The light reflected from or near the pearl’s surface, evaluated by the intensity and the sharpness of reflection.

  • Excellent (reflections appear bright and sharp)
  • Very Good (reflections appear bright and near sharp)
  • Good (reflections are bright but not sharp)
  • Fair (reflections are weak and blurred)
  • Poor (reflections are dim and diffused)

Surface – Blemishes or irregularities confined to the pearl’s surface, taking into account the size, number, nature, location, visibility, and type of surface characteristics.

  • Clean (blemish-free or containing minute surface characteristics that are difficult to see)
  • Lightly Spotted (only minor surface irregularities visible)
  • Moderately Spotted (noticeable surface characteristics)
  • Heavily Spotted (obvious surface irregularities that might affect durability)

Nacre Thickness – Average nacre thickness measurements for bead cultured pearls are optional descriptions on GIA reports. However, in cases where the nacre coating on a bead cultured pearl is too thin and/or damaged thereby potentially impacting durability, then GIA reports will clearly note this fact.

Matching – The uniformity of appearance in strands and multi-pearl pieces.

  • Excellent (uniform appearance and drilled on-center)
  • Very Good (very minor variations in uniformity)
  • Good (minor variations in uniformity)
  • Fair (noticeable variations in uniformity)
  • Poor (very noticeable variations in uniformity)
  • Not Applicable (for single pearls and certain intentionally mismatched items)
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