STORY B SHEUNG Lustre is the light and the life of the pearl. THE pearl is considered the most feminine of all gems; it shines like the moon, is soothing to the eyes and pleasing to the heart. While nacre is the very essence of the pearl (as discussed in our last PearlTalk), the spirit of the pearl lies in its lustre.
What makes one pearl more lustrous than another? Pearl nacre has a direct impact on pearl lustre. When the nacre is sufficiently thick, and the layers of nacre crystals are evenly constructed to show a regular pattern, a good amount of light will be reflected from the pearl surface as well as refracted from the deeper layers of nacre to give a bright yet soothing lustre.
The better the nacre quality, the higher the amount of light reflected, and the more intense the lustre. However, if the nacre is thin, or the layers of nacre crystals show an irregular structure, the pearl will have a chalky appearance that is dull and lifeless.
How to qualify lustre? Depending on the intensity of light reflected and refracted from the pearl, the lustre can be graded as excellent, good, medium and low.
Excellent lustre refers to pearls having a metallic shine. The metallic shine can be so intense that the pearls look like liquid mercury. Good lustre is when you look into a pearl and see the reflection of yourself in sharp contrast. When you see a blurred reflection of yourself from the pearl, the lustre is considered medium. When the pearl reflects little or no light, and the reflection is hardly discernible or non-existent, it is of poor lustre.
Different types of pearls have varying degrees of lustre. Generally speaking, good quality akoya pearls with evenly constructed nacre crystals have the highest lustre. Why? This is because the crystal tablets are relatively fine in akoya pearls. To obtain final layers of fine crystals, pearl farmers harvest the akoya pearls after the winter season, when the cold water slows down the secretion of nacre, and the nacre tablets formed are finest and most compact.
In warmer water, nacre growth tends to be faster and more abundant, but the nacre crystals may not be as compact and evenly constructed.
South Sea pearls tend to have a more silky glow. Those pearls which possess a metallic lustre are rare and are highly sought after. Black pearls have varying degrees of lustre depending on the structure of the nacre, and it also depends on whether the pearls are grown in cooler or warmer waters.
Freshwater pearls are consisted entirely of nacre, and do not have a translucent shell bead inside as in marine pearls to allow some light to travel through. They tend to have a silky to milky lustre. Metallic lustre is very rare among big-size freshwater pearls.
Keshi pearls are irregular in shape and have a special orient that is not often observed in smooth-bodied pearls. Orient is a play of rainbow colour which occurs when the white light refracted from the pearl is split into various colours. Orient is most common in irregularly shaped pearls because the uneven surface of the pearl is conducive to the iridescence effect.
How does lustre affect the value of a pearl? Lustre is a very important factor when evaluating pearls. Generally speaking, a 15mm round pearl is rarer and therefore more valuable than a 14mm round pearl. But if we take into account the lustre of the two pearls, the 14mm round pearl with a high lustre is rarer than the 15mm round pearl with a medium lustre. Thus you will find a higher price tag on the former.
Pearl experts will agree unanimously that nacre and lustre are the two most important criteria when selecting a pearl. A pearl with a thin nacre and a dull lustre, no matter how big, how perfect its form, and beautiful its colour, can never be considered a quality pearl.
Some friends told me that they were not comfortable wearing glittering jewellery. Too high profile, they explained. Years after, I saw one friend wearing a pearl pendant. I teased her, "Hey, you are wearing jewellery!" "No, my dear, it is a pearl," she said. I understand perfectly the subtle nuance of her statement. S
