How to grade pearls

Uncommon pearls uses the ‘A-AAAA’ Grading System for our Freshwater pearl jewelry. With A-AAAA Grading Systems, ‘A’ represents the lowest, commercial grade pearls. ‘AAAA’ denotes the finest pearl quality of each yearly harvest.


There are seven value factors when judging a pearl's quality: lustre, size, shape, colour, surface, nacre and matching.

 

1) Lustre :

Pearls with thin nacre usually have low lustre and can appear chalky, but the thickness of the nacre layer is not the only factor that determines the lustre. The tightness of the layers is the biggest factor in determining the lustre of a pearl; in short, even if the layers are very thick, the lustre of a pearl can be brilliant or pale.

  • Excellent, Outstanding lustre, deep mirror-like reflection and clarity
  • Brilliant, Nice sharp and clean reflection
  • Very Bright, Nice and good reflection
  • Bright, Nice light reflection, reflection image slightly fuzzy
  • Pale, Reflections are faint, not vivid and foggy, cloudy
  • Poor, Reflections are weak, dull and diffuse

 

2) Size

The ultimate size of a pearl depends on several variables:

  • The size and health of the mollusc that produces it.
  • The size of the nucleus.
  • The time spent immersed in the water.
  • Other factors including climate and nutrients present in the environment of the the mollusc.

 Size of round pearls

  • Freshwater - 1 to 14mm
  • Akoya - 2 to 10mm
  • Tahitian - 9 to 14mm
  • South Sea - 8 to 20mm

Size of irregular pearls (Baroque edison pearls)

Irregular shaped pearls can reach a length of up to 50mm.

As with other gems, the larger (in diameter) a pearl is, the more scarce it tends to be and the higher its cost becomes.

However, this rule does not apply in all cases. A flawless, high quality, small diameter pearl is more valuable than a poor quality, large diameter pearl. Thus, the final value of a pearl depends on the appropriate combination of different value factors.

 

3) Shape :

  • Perfectly round : Completely spherical without flat parts or notches (up close inspection (less than 6-inches) will reveal nearly perfectly round pearl shapes.)
  • Round : Variation of diameter being no more than 2% (the shape will be round to the eye from a distance of 6-inches approximately)
  • Slightly Off-round : Practically round to the eye (Upon close inspection (less than 6 inches), you’ll begin to notice a slight off-round shape to some of the pearls, however this is not the case for all the pearls in the strand.)
  • Near round : Slightly semi-round, elongated or flattened.
  • Oval : Egg-shaped, slightly rounded and oblong.
  • Button : Symmetrical, flattened on one side
  • Drop : Rounded pear shape.
  • Semi-baroque : Slightly oval, irregular. Button or drop shape.
  • Baroque : Quite capricious and asymmetrical shapes.
  • Demi-perles : Hemispherical pearls glued to the shell, such as Mabe pearl

 

4) Color

Pearls come in an array of stunning colours. From white, cream, pink, yellow, green, blue to black, there are so many shades in between. In addition, pearls often display delicate overtones, such as green, blue and pink. Many trade terms, such as apricot, aubergine, golden, lavender, peacock and pistachio, are also used to vividly describe pearl colours.

The high-value colours for Akoyas are silver and white. For freshwater pearls, they are white and lavender. Peacock and aubergine are the treasured colours for Tahitian pearls. For South Sea pearls, the most prized colour is deep golden.

Colours are usually a personal preference and they do not affect the quality of a pearl.

 

    5) Surface:

    The surface condition of a pearl affects its value. When other value factors are equal, the fewer and smaller the blemishes are, the more valuable the pearl is. In an ideal world, pearls would be free of all imperfections. But in reality, a perfectly clean pearl is a rare treasure.

    What is important to know is that as the diameter of the pearl gets larger, the probability of a flaw or of the pearl being imperfectly round increases; Large, flawless and excellent lustre pearls are extremely rare, the price of such a pearl will reach very high levels due to the rarity affecting the value. Therefore, most consumers must accept that the pearls they buy have some degree of imperfection in some respects.

    Even if there are minor imperfections on the surface of the pearl, if the pearl is large and its lustre is high, these positives will mask some minor imperfections; simply put, excellent lustre goes a long way to minimizing the imperfections on the surface of the pearl.

    • Clean (Perfect to Almost Perfect)

    1. Perfect : Their blemish rate is less than 1-3% overall, smooth and clean surface, but they might have textured surface due to their layered nacre structure.

    2. Almost Perfect : The surface has some winkles, small pits, smooth overall, not noticeable if you don't look closely. The blemish rate will be between around 5%

    • Slight imperfections (Very Slight to Slight Imperfections) Wrinkles or pinholes and small bumps on the surface, which are not obvious when worn and are not visible from a social distance
    • Moderate imperfections: Shows visible defects on the surface.
    • Heavy imperfections: Obvious defects on the surface of the beads, the durabilities could be affected.

     

    6) Nacre

    The nacre consists of:
    • 85% calcium carbonate
    • 12% organic matter,
    • 3% water.

    Nacre is the natural substance produced by a mollusc to form a pearl. The quality of nacre directly impacts the value of a pearl, especially in the case of saltwater cultured pearls where shell bead nuclei are present. The thicker the nacre is, the more durable the pearl is. The tighter the nacre is, the more smooth and exquisite the pearl is.

    There are three categories defined:

    • Acceptable : The nucleus is invisible.
    • Nucleus Visible : The nucleus is visible through the nacre.

    • Chalky appearance : The pearl has a dull, whitish appearance.

     

    7）Matching

    Matching is an important value factor when assessing more than two pearls. It needs to take all the other value factors into account and achieve harmony in terms of size, shape, colour, lustre, surface and nacre.

    A few examples of variations in matching:

    • A round pearl necklace may be slightly smaller at the end of the strand.
    • Each pearl in a necklace may have a slight colour difference.

    To create an excellent matched piece, we have to sift through thousands of pearls to find the ones that are well matched and this requires an enormous amount of skill and labour.

    BUT sometimes pearls are deliberately mismatched to create a casual and fun look. As long as the design achieves a balanced and harmonious look, the jewelry piece can still be very desirable.

     

    Pearl Grading scale, please click here