Pearl Quality Factors
Size
Each type of pearl has a general range of sizes they can grow to be. For example, South Sea and Tahitian pearls can grow to be as big as 13mm in diameter, while freshwater pearls might be anywhere between 2-7mm. Somewhere in between those two are Akoya pearls, which can be 6-8.5mm in diameter.
The most popular pearl jewellery pieces are made of 7-8mm pearls. Naturally, larger pearls look great when strung on a necklace, while smaller ones are better for earrings or detail work. Of course, larger pearls are more expensive as well.
Shape
Even though many people are most familiar with the image of a strand of perfectly round pearls, they can come in many different shapes. Many pearls are not, in fact, perfectly symmetrical and come in various off-kilter shapes, which actually add to their unique charm. The roundest pearls are usually Akoya, Tahitian, and South Sea pearls, so they’re often in high demand.
However, even freshwater pearls can manage to be round, though they often tend to be more oval. This shape is pretty standard, as pearls can even naturally be teardrop and baroque-shaped. In fact, off-round shapes, like elongated or bumpy pearls, are more popular than ever.
Colour
Pearls naturally come in several body colours, including white, yellow, pink, and black. They can also be cream and silver, which is what we call pearls that are mostly white but appear to have a somewhat warm or cool tone. Aside from general body colour, many pearls also have a different colour as a sort of overtone. So, a pearl might be white, but it could have a golden overlay when the light hits it.
Even though white is by far the most popular colour for pearls, any of these colours would add a new element to a look.
Lustre
Lustre is what we call a pearl’s shine, and it’s caused by the layers of nacre that an oyster packs around a stimulant. So, bigger pearls are also shinier because they have more layers of this calcium carbonate crystal. So, if you’re looking for shine, you’ll definitely want to turn your attention to the bigger pearl varieties, like the South Sea and Tahitian pearls. Typically, experts measure lustre by observing the reflectivity of the pearl, which is why they photograph pearls under square lights. The pearl with the square reflection is higher in lustre than the one with a rounded one.
Quality
The overall quality of a pearl depends on all of the factors we already mentioned and many more. When a shellfish creates a pearl, it applies the nacre in smoothly packed layers. If pockets of air remain trapped between layers, the pearl can be prone to breaking. That’s why smoother pearls are more valuable –they won’t break easily. Of course, there’s no way to actually promote smooth nacre layering once the stimulant is inside the oyster.
Most jewellers take care to create pieces using pearls of a similar size and quality. Or, in the case of graduated strands, we might string the pearls by a gradual increase in size. Since every pearl is different, jewellers carefully select similar ones going by colour, lustre, and surface quality and markings.
It’s good to mention that the industry doesn’t actually have a set grading system for pearl quality. However, Appleby ensures that each pearl meets our high-quality standards.
