Pearl Quality Guide

The important factors

What Determines Pearl Value

Several factors determine the value of pearls, including size, shape, colour, lustre, nacre thickness, surface quality, and pearl matching. However, rarity also significantly affects pearl price. The rarer the pearl, the more valuable it is.

Pearl Quality Factors


Measure the diameter of round pearls in millimetres. Measure other pearl shapes by both width and length. Rarity makes larger pearls more valuable, as long as other quality factors are equal. The rarity of a pearl's size depends on the type of pearl. South Sea pearls larger than 17mm are rare, while Akoya pearls larger than 9mm are considered rare.


Growing a spherical pearl, especially one of larger size, is difficult. When other factors are equal, the rarity of round pearls makes them the most valuable of all shapes. However, other shapes such as drop and oval can also be valuable if they are symmetrical. Baroque pearls are irregular and asymmetrical in shape and are usually cheaper compared to other pearl shapes. However, their value may increase if they have unique iridescent colours and meet the standard for other quality factors.


Pearls come in a variety of colours, ranging from soft pastels to bold dark tones. The colour of a pearl is made up of three components: body colour, overtones, and orient. Lustrous, classic white pearls, intense gold pearls and rare Tahitian colours are in high demand. Cream colour pearls are less favourable. Just like other factors, the value of a pearl's colour depends on demand and supply during the harvesting period


The lustre of a pearl refers to the way it shines and glows from within. Pearls with high lustre have a strong and sharp reflective surface, while those with low lustre appear chalky and dull. Although lustre and nacre thickness are separate value factors, they are somewhat related. If the nacre layers are produced evenly and consistently over a long period of time, even a pearl with a thin nacre coating can be lustrous. On the other hand, some pearls may have thick nacre coatings but low lustre if each layer is produced too quickly during the growth process.

Nacre Thickness

Nacre is the layer of substances secreted by mollusks that surround the bead nucleus to form pearls. This is important in nucleated cultured pearls. If the pearls are harvested too early, the oyster will not have time to coat them with enough layers of nacre. Thick nacre not only makes a lustrous pearl, but also makes it more durable. South Sea Pearls usually have a thicker nacre than Akoya pearls. As for freshwater pearls, nacre thickness is not that important for non-nucleated pearls. But for the nucleated ones, it is usually thicker than Akoya pearls because of their longer cultivation period.

Surface Quality

A high-quality pearl has a smooth, even surface. The fewer imperfections and flaws it has, the more valuable it is. However, it is normal for pearl strands to have some flaws, which are more acceptable. In contrast, blemishes on single pearls tend to be more noticeable and can affect the value of the pearl.


Pearl matching is important for jewellery that requires two or more pearls, such as earrings and necklaces. The value of these pieces depends on how well the pearls blend together in terms of all the above factors. High-quality, well-matched pearls are extremely rare. Today, multi-colour pearl necklaces are also in demand. Even if the combination includes multiple colours, the value will be high if all other factors match.

The highest quality pearls have a mirror-like, reflective surface in which you can clearly see even your own reflection.


In conclusion, the quality of pearls is determined by various factors including size, shape, colour, lustre, nacre thickness, surface quality, and pearl matching. The rarity of the pearls also plays a role in their value. By understanding these factors, you can determine the quality and value of pearls.

Explore More About Pearls

If you'd like to continue exploring the world of pearls, visit our pages on pearl grading and pearl necklace length guide. There you'll find a wealth of information and beautiful examples of these different characteristics.

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