7 Factors for Pearl Quality Appreciation

7 Factors for Pearl Quality Appreciation

2 Major mistakes…

Pearls are kind of mysterious because of the colour and lustre it has. We describe the lustre as ‘orient’ effect or ‘iridescence’. In physics, it is due to reflection, refraction, interference and diffraction of light rays caused by the platelets of aragonites (which are actually the mineral form of calcium carbonate).

One major mistake when buying pearls is to see the size of the pearls. Larger doesn’t mean better. In fact, some pearls though large, have only a very thin layer of nacre. It is large because of the bead nucleus used to produce the pearl.

The other major mistake for consumers is the failure to ask for the origin (or the make) of the pearl, whether it is south sea pearls or freshwater pearls. Instead, they ask about the price first. As with many other gemstones, the price should not be the determining factor for a purchase. Important factors to consider first should be the authenticity and the quality of the gem material.

7 factors of pearl quality

#1 Shape

The most commonly appreciated shape is round. If the pearl is round, we have to consider the percentage roundness of the pearl. Generally, south-sea pearls are almost perfect in roundness, as these are cultured with round mother-of-pearl shell beads. Other shapes include button, tear-drop, baroque, oval etc.

There are other shapes that freshwater pearls produces, through human intervention. Some shapes include crosses and fancy shapes. These can be produced with carefully cut mantle tissues from the donor mussels.

Tip: Choose one that is suitable for the occasion, or one that you think matches with your personality. My personal favourite is still round.

#2 Lustre

Lustre in gemology is defined as the quality of light reflection on the surface of a material. It can be dependent on the quality of polish and the hardness of that material. As mentioned earlier in this post, lustre for pearls is described as ‘orient’. Sometimes, it is simply described as ‘pearly’. Pearls have a hardness of between 2.5 to 4.5 on Mohs’ Hardness Scale. It has a range of hardness because of the quality of nacre. The production of cultured pearls is dependent on a few factors, such as the quality of implantation of mantle tissue (and bead, for south-sea pearls), the quality and environment of the waters in which the mussels or oysters are allowed to grow, the quality and health of the donor and host mussels or oysters as well as the length of growth of the pearl in the shells (i.e. thickness of nacre). Much research and trials have to be carried out on pearl culturing techniques but many are kept confidential with a high level of trade secrecy (it is necessary as pirates are still pretty much active at the seas today).

Tip: Pearls with higher lustre has higher durability compared to pearls with low lustre as it can get damaged by scratches or other physical forces more easily.

#3 Surface quality

In other words, blemishes on the surface of the pearl. Scratches are easily seen on pearls with poor lustre, or pearls with thin nacre layer. Depending on the condition of growth, pearls with poor surface quality can also appear to have lots of pitting or ‘pot-hole’-like blemishes. The more numerous there are of these blemishes, the lower the surface quality of the pearl. This factor is also the most obvious and irritating to the consumer’s eyes.

Tip: There is no pearl that is 100% prefectly free of surface blemishes. Choose one that is pleasing to your eyes.

#4 Nacre thickness

To be honest, for a layman consumer, it is very difficult (or near to impossible) to check the thickness of nacre. Pearl nacre is essentially the layers of mineralised (or crystallised) calcium carbonate and conchoilin formed during the formation of the pearl. Pearls are formed due to an injury in the oyster or mussel. This is contrary to the old belief that pearls are formed when a sand or irritant gets implanted into the shell. As these are live animals (the oysters and mussels), they have a natural protective mechanism that will protect them from external harm. So if the sand gets into the shell, the animal will natural reject the ‘intruder’. Pearls are formed when these ‘intruders’ (such as sand), cause an injury to the animal tissue. The natural mechanism that will then occur, is to form a pearl sac, and from there protect itself from further harm by the ‘intruder’.

The following pictures show two types of cultures pearls: Freshwater cultured pearls and Saltwater cultured pearls. As described earlier, freshwater cultured pearls are non-beaded nucleated cultured pearls, while saltwater cultured pearls are beaded nucleated cultured pearls. The pictures show cross-section of a collection of pearls by Prof. H. A. Hänni, who is also our good friend and mentor from Switzerland.

Tip: Nacre thickness and pearl lustre is very closely related. Poor lustre is often due to thin nacre. Therefore, make your observation by looking at the lustre, but not forgetting that there will be times when thin nacre produces good lustre due to high quality of production. (IMHO: ANYTHING IS POSSIBLE!)

#5 Size

Another factor that is most appealing to consumers is the size of pearl. I have heard many people commented that they liked baroque pearls because they are big, and most likely cheaper than big round ones. It is quite obvious that the larger the pearl, the higher the value. Even for cultured pearls (so called with ‘human intervention’), it is also rather difficult to produce a large pearl more than 15mm.

Pearls sizes are usually described in millimeters, by measuring the diameter of the pearls. In the trade, pearl weight is sometimes used and the unit of measurement is in momme, an ancient Japanese measurement still used in today’s context.

1 momme = 18.75 carats = 3.75grams

Tip: If you’d like, bring along a measuring guage to check the size of the pearls!

#6 Colour

Colour of pearls can range from white to gold to green to black. Due to the nature of pearls, it most often has secondary colours. Black pearls are rarely pure black for example. They always come with a secondary colour of green, blue or purple. Time is required to train the eyes for the colour grading of pearls. Our eyes become ‘white-balanced’ after a while when looking at something for a period of time. Hence, to determine the colour of a pearl is not an easy task. The picture below is an example of colour variation in pearls.

Tip: Colour preference is a very personal factor. As a consumer, I personally think you should listen to your heart, rather than listen to a pearl dealer.

#7 Matching (for pearl strands and earrings)

This could be a no-brainer, but some creative designers like it mixed up, with different colours, shapes and sizes. Gestalt psychology (a modern study of perception), the human eyes are perceive things that are symmetrical, balanced and proportionate to be more superior aesthetically. According to this concept people do not perceive their environment in terms of discrete visual elements but rather in terms of configurations. (Sources: http://www.britannica.com/science/Gestalt-psychology ; http://bit.ly/1Rta0yP)

In pearl strands, earrings or any other multi-pearl jewellery, the value increases as the consistency of the pearls increases. The more matching the pearls are, the more valuable it is. This is due to a few factors like the rarity of getting a strand of 40 pieces of pearls that have the same size, same colour, same lustre, same nacre quality and same surface quality. It is difficult to produce (culture) a whole lot of pearls with the same quality factors. The effort to collect and put them together is immense and requires a trained and experienced eye to do so, especially in matching the colours. The longer the strand and the larger the pearl, the harder it is to put together.

Finally, in order to give a pearl its value, the authenticity is very important, other than the 7 factors mentioned above (7 is a lot to grasp already!) When we talk about authenticity, what we really mean is the originality of the pearl. If it is a natural pearl, is it a natural-natural pearl? Or a freshwater pearl? Or a saltwater pearl (south-sea pearls as some put it)?

If it is any of the three mentioned above, has the pearl been treated in any way? Some treatments we want to consider are: dyeing, coating, irradiation, heating etc. Always remember ask the jeweller or pearl dealer for all these technical information.

I was inspired to write this article because one of the interviews I had on Singapore mandarin Channel 8 was on repeat telecast just yesterday. My friends caught me on TV and sent me photos and youtube link to the variety show. Our institute has collected many samples for an upcoming Pearl Grading course which will be launched some time this year. I believe knowledge is never-ending and we keep learning to improve ourselves and also learning from the wisdom of others.

This article was first published on LinkedIn.

About the Author

Loke Huiying is the Director of Far East Gem Institute and the Founder of The Gem Museum in Singapore. Being in a family business, she met with many roadblocks while managing and developing the business. Through these setbacks and many other successes, she has put together a 4C method – clarity through consultation, credibility through certification, connection through networking and commitment through education. She has also written “10 Steps to Gem Identification” ebook, to help aspiring gemologists take the first step to learn about gems and gemology. With these, she believes that it would help many others who want to build a trusted and successful gems and jewellery business.