Mother of pearl is the common name for an iridescent nacre coating, a blend of minerals that are secreted by oysters and other mollusks and deposited inside their shells, coating and protecting them from parasites and foreign objects.
Mother of Pearl vs. Pearl
A pearl is also composed of nacre. When a pearl is formed, a layer of nacre is deposited around a tiny particle that becomes lodged in a mollusk, either naturally or inserted by a human. Eventually, this nacre builds around the small object and becomes a pearl. This outer coating of a pearl, despite being composed of nacre, is not referred to as the mother of pearl.
For jewelry, mother of pearl usually references the thin nacre coating that is adhered directly to the mollusk's shell. However, not all mollusk shells have a nacre coating. The primary distinction between a shell that has a mother of pearl coating and a shell that does not is the iridescent quality.
Mother of pearl has a very distinct multi-colored effect and a faint glow similar to other optically impressive moon-like gemstones. Non-nacre mollusk shells will look more like smooth and uniform porcelain.
When the term mother of pearl is used in jewelry, it does not refer to all nacre including a pearl's coating. It instead refers to the nacre that coats the inside layer of the mollusk shell. Mother of pearl set into jewelry is comprised of only a thin layer of sediment similar to a boulder opal. This thin layer can be carved or cut into cabochon-like shapes.
Like pearls, mother of pearl jewelry falls in the group referred to as organic jewelry—jewelry that originates from a living creature, plant or organism.
Mother of pearl jewelry and pearl jewelry look very different in a number of ways. Mother of pearl jewelry can have much larger focal pieces than pearls since the substance takes up a whole shell's interior. Most mother of pearl is found in fine jewelry settings. Pearls are usually drilled and strung, rather than set. Pearls are thick, rounded gems that max out at a certain size. Mother of pearl is thin and slightly rounded.
Mother of Pearl Value vs. Pearl Value
Natural pearls are more expensive than a natural mother of pearl gem because pearls are significantly rarer. Think of it this way: all nacre producing mollusks will have a mother of pearl coating inside their shell that can be used in jewelry. However, of those nacre producing mollusks, only a small percentage of them will have a small particle naturally make its way inside their shells.
Manmade pearls and mother of pearl are both significantly less expensive than their natural counterparts. However, larger manmade pearls will be more expensive than a similar mother of pearl piece due to the extended time they take to form.
Despite the wide availability of mother of pearl due to pearl farming, it is still underused in the jewelry industry compared to its use in previous jewelry eras.
Much of the aversion to using mother of pearl in designer jewelry may come from the unwillingness to support unsustainable and unnatural pearl farming practices. Using mother of pearl in jewelry is looked at in the same way using coral or ivory is: unfavorably.
This is why the most desirable mother of pearl jewelry is often antique or vintage. Some jewelry companies are taking note and are starting to use more widely accepted pearl farming practices.
If you're looking to purchase mother of pearl in an environmentally friendly way, be sure to seek out companies that ensure safe, ecologically sustainable ways of collecting their material.