Classification of Tahitian, Akoya, Australian and freshwater cultured pearls

Pearl classification - from A to ... A

What's behind these initials and how to find your way around

Depending on whether you use the Polynesian or the international classification, the same letter designates the best or the worst quality.

To get you started, here's an equivalence table between the two standards:

As you can see, A quality according to the Tahitians is far superior to A quality according to the international standard 😊

Now that you've mastered the standards, let's see what they really mean...

Pearl classification criteria

Unlike fine wines, pearls cannot be tasted, but they can be appraised according to a method developed by the GIA (Gemological Institute of America), which consists of evaluating the four main characteristics of a pearl to give it a final grade.

These characteristics are :

1 - Luster

Luster is the most visible aspect of a pearl's beauty: its shine.

These changing reflections are produced by light penetrating the pearl's different nacre layers.

But although pearls with a very thin nacre often appear dull, thickness is not the only explanation.

The arrangement of the mother-of-pearl platelets and their translucency are decisive factors.

The faster nacre is produced, the less translucent it will appear.

Although pearl farmers are constantly improving their techniques and the quality of their production, it is still Akoya white pearls that possess the highest level of luster. Experts believe that the cold waters in which they are produced allow the pearls to accumulate nacre layers more slowly, thus increasing the likelihood of achieving excellent luster.

According to the GIA, 4 categories of luster are accepted:

Excellent (very bright to brilliant): Reflections are bright, vivid and distinct.

Good (brilliant): Reflections are bright, but not vivid. The edges of the pearl are slightly hazy. 

Pale: Reflections are faint, not vivid and misty (cloudy). 

Poor: Reflections are weak (dull) and diffuse.

Where Akoya pearls have a glossy, almost mirror-like sheen, others like Tahitian pearls have a more typical satin sheen.

2 - The surface

Perfection is rare, and pearls produced by living organisms are no exception to this rule.

If you have in your hands a pearl absolutely free of the slightest flaw, cherish it - it may be worth a small fortune.

If you have several identical ones... ask yourself questions about their origin. Each pearl is unique, and only those made by human hands have the beauty of counterfeit...

For the GIA, 4 categories exist:

Clean (perfect to near-perfect): Pearl without any imperfections, immaculate or containing tiny features. The latter are very difficult to locate, even if the observer is highly trained.

Slight imperfections (very slight to slight imperfections): The pearl shows minor surface irregularities when observed by a trained eye.

Moderate imperfections: The pearl shows visible features on its surface.

Heavy imperfections: Obvious irregularities on the pearl's surface. Its durability may be affected.

These imperfections, together with their extent, are used to place a pearl on the grading scale:

3 - The shape

When we talk about pearls, the image of a ball immediately springs to mind, but pearls come in all shapes, from the most classic to the most bizarre. After all, oysters are only supplied with a graft, but never with a blueprint - nature is free to do as she pleases...

Professionals generally agree on 7 families of shapes:

Round: the pearl is visibly round to the naked eye.

Semi-round: Practically round to the naked eye. The pearl may appear slightly elongated or flattened.

Oval: Symetrical, elongated and rounded.

Button: Symmetrical, flattened or slightly flattened. May be dome-shaped (high or low).

Drop: Symmetrical, rounded pear-shaped. May be elongated or short.

Semi-baroque: Not symmetrical, slightly oval, irregular. Button or drop shape.

Baroque: Non-symmetrical with a noticeably irregular appearance.

When a pearl is fluted (grooved) all around, it's called a hooped pearl.

4 - Nacre thickness

An oyster forms up to 10 layers of mother-of-pearl per day, each micron-thick. It generally takes 2 to 4 years to obtain 1 good-sized pearl.

In the case of Tahitian pearls, the government of French Polynesia has established a minimum nacre thickness of 0.8mm for a Tahitian cultured pearl (usually achieved within 18 months). All pearls with a nacre thickness of less than 0.8mm are de facto banned from export, and generally end up as powder for use in cosmetics.

Mother-of-pearl quality is classified into 3 categories:

Acceptable: The nucleus is invisible.

Visible nucleus: The nucleus is visible through the nacre.

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

The question of nacre thickness obviously doesn't arise for freshwater cultured pearls, because in the absence of a nucleus, there is... only nacre

Now all you have to do is assign a grade to each of the four characteristics presented above, combine them all and you'll know how to grade pearls like a true GIA expert 😂