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A Comprehensive Guide to Cultured Pearl Quality

There are many attributes that should be taken into consideration in order to assign a value to an individual pearl. We will talk about these and give you the information you require in order to make a good selection.

Size
As In the case of many other gemstone: the bigger its size is, the greater its value. Depending on the type of jewelry you plan to use, small pearls are more adequate than large ones for -let's say- rings and studs.
Larger sizes are less abundant so they are able to fetch a much better price. Once a pearl attains a size of 10 mm it can command a higher price, but there are other breakpoints as well: 12, 14, 18 and 20 mm. This means that the price of a pearl may as well double from the size previous to that break point.

Large Cortez Pearls

Chose the size of the pearl depending on your needs and budget. Selecting a 9.9 mm pearl is a great choice because you do not pay the increase in price and yet it looks basically the same.

Luster/Lustre.
This is an attribute you should take seriously into consideration when purchasing a pearl. A pearl's luster is the warm, silky, glow of the pearl. But do not confuse luster with "shine". A polished piece of steel is very shinny, but it is not lustrous. Luster is given by a combination of "surface luster" (superficial shine) and "deep luster". 

Pearl Luster Comparison: Akoya, Freshwater, Tahitian & Cortez
Of course, the higher the luster of the pearl, the more valuable it becomes. Thinly covered cultured pearls are always dull and lackluster, since this effect is given by the many millions of thin layers of nacre. A pearl without luster is as beautiful as a polished bead of clam shell.
Nowadays it is a very normal procedure for pearl farmers to send their pearls to be polished. Polishing adds more superficial luster to the pearl (but it cannot give you the much more desired "deep luster" effect) but this also takes away several coatings of nacre.
Good quality pearls do not need polishing and are -as a matter of fact- deeply affected by this process (they can actually loose some of their superior natural luster).

Orient/Overtones.
This is one of the most beautiful effects found on a pearl, and the hardest one to explain or describe. This effect is given -in part- by the pearl's nacre thickness, its spiraled surface and the quality of its nacreous (Aragonite) crystals.

Explanation of Orient Overtones - Iridescence on Pearls

This visual effect is seen as a series of concentric rings of deepening color. Sometimes it looks like a "halo" surrounding the outer diameter of the pearl. A pearl with such an effect will never be mistaken as a fake-pearl nor as a freshwater pearl, and it is highly coveted.

Orient Overtone Comparison in Pearls

The word "orient" is attached to this effect in lieu of a centuries old fact. To the Romans -who loved these Gems- pearls came from two different sources: freshwater pearls (harvested from European rivers and lakes) and "Oriental Pearls" that were imported from the Middle-East (the "Orient" for Romans).
To the Romans, "Oriental Pearls" came mostly from the Persian Gulf and sometimes even from Asian countries...and those were mostly saltwater pearls.

Shape.
Truly 100% round shaped pearls are much more difficult to obtain, thus they command a much higher prize. Only from 5 to 25% of a pearl harvest come out round to semi-round in shape.
So, a round shape takes first place in value, followed by "off-round" (about 2-5% of the pearl's shape is not-round), semi-baroque (symmetrical shapes: drops, buttons, ovals) and finally baroques (asymmetrical pearls).

Different Pearl Shapes
Semi baroque pearls are highly coveted in some countries, especially in the drop shapes, where they are known as "cabochons", "tears" or "pears". They are very popular in drop-style jewelry and used mainly in pendants and earrings. Baroque pearls do not have a definitive shape, being always irregular in their skin/surface, coloring and appearance. Sometimes, keshi pearls are easily mistaken with baroques, the main difference being the presence of a nucleus in the latter. Baroque pearls are very unique, so they can give a more natural look to jewelry.

Baroque Cortez Pearl

So, as you can see, many pearl shapes exist, but people tend to identify a pearl as being "round". This is due to the fact that the Japanese were the World's leading suppliers of cultured pearls (today, the main producer of pearls is China), and they are able to produce many round pearls thanks to:

  • The fact that they have a very high production of cultured pearls: around 20 metric tons of Akoya pearls per year, thus they have a higher chance at obtaining more rounds. 
  • They have very good seeding technicians: and these play an important role in pearl quality. 
  • They grow their cultured pearls from 4 to 8 months only: this does not allow their pearls to "deviate" from the nuclei's round shape.


Purity/Surface Defects.
This attribute is also known as the "skin purity" of the pearl. As it can be expected: the lesser the number of imperfections on the surface of the pearl, the higher its value. A pearl with no visible defects (zero imperfections or flaws) can be considered a Gem (but it must also have nice luster and good orient/chroma).

Pearl Surface imperfections or Flaws
Sea of Cortez Pearls are only available in the following grades: Gem, A and B.
An "A" grade pearl has 1 to 3 small defects (less than 10% of its area), a "B" grade has anywhere between 3 and 7 small imperfections (10-33% of its area). "C" grade has large and visible spots on most (33-66%) of its surface. Beyond this amount of defects, they can be considered a "D" grade or even "Reject" pearls.

Gem+++ Grade Cortez Pearls
It is fairly common for a pearl to have surface defects. After all, a pearl is a living creation, not a cold hard stone dug from the Earth. One should allow for defects in a pearl, just as we allow leather goods to have skin defects, without which they would look just like plastic...

Some common surface defects:
Missing Nacre:
This defect resembles an "animal bite" on many occasions. It is caused by a secretory problem in the mantle (patches of cells within the pearl sac become abnormal and cannot secrete nacre, or will produce calcite instead). If this defect appears on a large proportion (over 30%) of the pearl, it should be considered a reject.

Spots/Protein Deposition:
These spots appear when there are secretory problems in the mantle (patches of cells within the pearl sac become abnormal and cannot secrete nacre, and will produce protein instead). These “spots” not only make the pearl look less appealing, but they may also indicate other structural problems...try to avoid these pearls.

Waves/Undulations:
Some people do not consider these to be a problem or defect, but consider them more like a natural pattern, as seen on many baroque pearls. Anyway, since the surface of the pearl appears to be disjoined (surface reflection or luster is diminished), the value of the pearl is lessened.

Pearl Petroleum:
Also known as “PePe”. This is the typical "juicy pearl". You drill or press hard on a given area of the pearl and a thin coating of nacre cracks/breaks and then nauseating brown ooze will come out. These pearls have a large amount of organic matter trapped inside, and should be avoided since most will eventually crack (unless the liquid has been extracted and the pearl has been evaluated for nacre thickness).

Other Defects
Cracks, peel-offs and deep bruises (mechanical scars) are not considered to be natural flaws. These are serious defects that turn pearls into junk. A pearl with a crack (or even a fissure) is damaged to a point where it will break apart. Pearls that loose some of their covering (usually, this only happens to thinly covered cultured pearls) will crack and expose their nucleus. Never -ever- accept those kind of defects on pearls.