When we think about pearls, we usually think of lustrous white orbs crafted by delicate oysters not unlike those we might find at the Oyster Bar at Grand Central, not far from our Manhattan offices.

So it was a bit of a surprise to some of our more junior team members when our Thai team shared the story of the melo melo sea snail’s beautiful tangerine pearl. These carnivorous mollusks, native to southeast Asia, can grow nearly a foot long. Their large pearl lacks nacre, the composite material that results in the iridescent effect so desired in most pearls. However, the material within melo melo pearls can create a gorgeous, shimmering flame effect within the pearl, seemingly illuminating the orange gradients from within.

What, then, is a pearl? The broad definition from the GIA includes the fiery melo melo pearl alongside the traditional, white or cream pearl that comes from oysters or mussels. Almost any mollusk can produce some kind of pearl, though the majority, known as calcareous concretions, lack the intrinsic beauty we find in pearls used for jewelry. Thanks to these natural variations, jewelry pearls can take on almost any color and shape to suit your jewelry. Overtones can supplement the main color, adding complexity and interest just like secondary flavors in a wine.

Let’s have a look at some of the primary ways pearls are developed for use in jewelry.

Natural (Wild) Pearls

The most rare and expensive pearls, natural pearls come in many shapes and sizes. They are developed naturally, without human assistance, as a microscopic irritant enters the mollusk and settles in the shell. The mollusk’s natural reaction is to form a pearl sac of mantle tissue around the irritation, eventually covering it and producing the pearl.

Most natural pearls are either recycled from existing jewelry or are gathered off the coast of Bahrain or Australia. Determining whether a pearl is natural or cultured requires a straightforward x-ray examination of concentric growth rings at the center of the pearl. At Insider Creations, our team meticulously checks to ensure that all natural pearls are responsibly sourced and certified.

Cultured Pearls

Cultured pearls are developed with human intervention. Primarily farm-raised mollusks are implanted with a small irritant – either another piece of mantle or a small bead. These mollusks, tended by workers, eventually develop a pearl around the irritant and are harvested for use around the world.

Unique among cultured pearls, keshi (or poppy seed) pearls are entirely made of nacre and thus have spectacular luster, albeit in unusual shapes. After their host mollusks reject the nucleus or are wounded, these pearls generate in unusual shapes without a nucleus at the core. These are especially popular in Japan, where they originated.

Imitation Pearls

Imitation pearls come in a variety of forms, shapes and materials. “Shell” imitation pearls are made from conch shell or mother-of-pearl, natural elements that make up the mollusk itself. Others are made from glass and coated with chemicals that imitate natural pearl’s color and shine. Though cheaper than natural or cultured pearls, imitation pearls still represent a degree of class and sophistication in jewelry. The most common way to identify an imitation pearl is to rub it against the teeth: imitation pearls are smooth, while natural and cultured pearls will typically feel very slightly gritty on the tooth.

Though many imitation pearls are made from elements of discarded mollusk shells, vegan pearls made without organic elements are also available.

What else do I need to know about pearls in jewelry?

Value is traditionally determined by luster, color, weight, size, surface flaws, and symmetry. Perfectly round or teardrop-shaped pearls are especially sought after, though they are quite rare. A well-formed oval, pear, or baroque (irregularly-shaped) pearl is also desirable.

Luster is the measure of how a pearl reflects and refracts light. These sharp, bright reflections come from the interaction of light and the many layers of nacre in a pearl. Holding all other factors equal, luster is often the key determinant of a pearl’s value. A pearl’s luster is rated excellent, very good, good, fair, or poor.

Nacre quality, depending on the type of pearl, can be critically important – and a major determinant of luster. The thickness of the nacre layers in a pearl helps to determine not just luster, but structural durability.

Color can vary wildly in pearls, though white or cream are most common. As noted above, orange and other alternative colors are growing in popularity for their unique qualities. Though not all pearls boast more than bodycolor, there are three key descriptors for pearl coloration:

Bodycolor is the pearl’s dominant color.

Overtone is one or more translucent colors that lie over a pearl’s bodycolor.

Orient is a sheen of iridescent colors on the surface of the pearl.

Weight is measured in carats or, in some regions, the momme, a unit developed and used by the Japanese for centuries. One momme is 3.75 grams.

Size, measured in millimeters, tends to range from 2-16mm.

Surface quality reflects the blemishes on the surface of the pearl: small scratches, ridges or misshapen spots that may be hard to conceal.

Matching is highly desirable in many string or combination pearls, though it is increasingly common to find mix-and-match pearls in a set.

This story is cross-posted on Medium.