Celebrated for its mesmerizing beauty, the Grace Kelly of gems is June’s elegant birthstone–the pearl. We previously discussed the pearl’s history and lore, and the different types of pearls. Now let’s delve into how a pearl’s value is assessed, and what to look for when purchasing a pearl.

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Though most known for creating the 4Cs and diamond grading standards, GIA also created a standard for describing pearl quality – the GIA 7 Pearl Value Factors™. These factors are:

1.    Size: Measured in millimeters,  and rounded to the nearest 0.5 mm

2.    Shape: Described as Round, Near-round, Oval, Button, Drop, Semi-baroque and Baroque

3.    Color: A combination of the pearl’s dominant body color, overtone and orient. Body color takes into account hue, tone and saturation. Overtone is a noticeable translucent color that appears to layer over the pearl’s body color. Orien
t is the mixture of colors shimmering just below the pearl’s surface.

4.    Luster: The light reflected from the pearl’s surface, evaluated by the intensity and sharpness of the reflection. Luster is evaluated according to the following scale:

  • 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

5.    Surface: Evaluated based on the blemishes or irregularities in the pearl’s surface, taking into account the size, number, nature, location, visibility and type of surface characteristics. Surface is rated by the following scale:

  • Clean – blemish-free, or containing minute surface irregularities that are difficult to see
  • Lightly spotted – only minor surface irregularities are visible
  • Moderately spotted – noticeable surface blemishes
  • Heavily spotted – obvious surface irregularities that might affect durability

6.    Nacre Quality: Nacre quality is determined by its thickness and layering. When the thickness of the nacre coating on a bead cultured pearl is too thin or damaged, appears chalky, or if the bead can be seen through the nacre, it may impact the pearl’s ability to sustain normal wear.

  • Acceptable – nucleus not noticeable; no chalky appearance
  • Nucleus visible – pearl(s) show evidence of bead nucleus through the nacre
  • Chalky appearance – pearls have an obvious dull appearance

7.    Matching: This measurement only applies to a strand of pearls, or jewelry pieces with multiple pearls, by assessing the uniformity of all the pearls in the piece.

  • Excellent – uniform in 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

Pearls are often treated to improve color, shape, surface appearance, weight and durability. Pearls are porous, which allows them to accept many treatments more readily than non-porous gemstones, while their softness permits them to be shaped fairly easily. Treatment processes may include bleaching, heating, dyeing, irradiation and coating to improve color; peeling to improve shape and or surface appearance; or filling and impregnation to increase weight or enhance durability.

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So how can you be sure about the quality of pearls you’re buying? GIA Pearl Reports provide in-depth information about detectable treatments, the pearl’s origin, its growing environment and the mollusk species that produced it. The report includes a quality description based on the GIA 7 value factors described above.

Please join us for the final installment of our June birthstone blog series where we’ll share valuable tips on how to care for your pearls!

Does learning about these factors help simplify your decision-making process? We’d love to hear from you!