I am no expert on pearls, but in this post I will share with you a bit of research I have done on pearls. Anyone seeking more detail or clarification would be well advised to consult with a certified gemologist and/or GIA (Gemological Institute of America). But here are a few interesting things I have found --
(side note: Many thanks to Jeffery Bergman on LinkedIn, who found some needed corrections and shared them with me...)
A pearl is an object produced when a mollusk produces layers of nacre (pronounced NAY-kur) around some type of irritant inside its shell. In natural pearls, the irritant may be another organism from the water. In cultured pearls, a nucleous is inserted (by humans) into the mollusk to start the process. The ideal pearl is perfectly round and smooth, but many other shapes (baroque, oval button and drop) can occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable. The necklace to the right is made with multicolor South Sea & Tahitian pearls, assorted gemstones and 24K Gold Vermeil; from OrientalEmpire on Etsy.
Historically, many natural pearls were found in the Persian Gulf; unfortunately, today, most have already been harvested. Natural (or wild) pearls, formed without human intervention, are very rare. Many hundreds of pearl oysters or mussels must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way pearls were obtained, and why pearls fetched such extraordinary prices in the past. Today, natural ‘pearling’ occurs mostly in seas off Bahrain (a country in the Middle East). Australia also has one of the world's last remaining fleets of pearl diving ships. Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry.
Cultured pearls are grown in pearl farms. The mollusks are raised until they are old enough to accept a nucleous, generally a polished sphere made from freshwater mussel shell. Through a delicate surgical procedure, the technician implants the nucleous and then the mollusks are returned to the water and cared for while the pearl forms. Not all produce a pearl; and not all the pearls are high quality. Over 10,000 pearls may be sorted before a 16” single strand of beautifully matched pearls is assembled. Pearls can be found in saltwater and in freshwater. There are also different types of mollusks that produce very different looking pearls.
Keshi pearls, although they often occur by chance, are not considered natural. They are a byproduct of the culturing process, and therefore don’t happen without human intervention. They are very small, typically only a few millimeters. Keshi pearls are produced by many different types of marine mollusks and freshwater mussels in China. Keshi pearls are actually a mistake in the cultured pearl seeding process. In seeding the cultured pearl, a piece of mantle muscle from a sacrificed oyster is placed with the nucleous (or bead) within the oyster. If the piece of mantle should slip off the bead, a pearl forms of a different shape. Therefore, a Keshi pearl could be considered superior to cultured pearls with a standard bead center. (Lovely Keshi pearl bracelet to the right is from TheSpiralRiver on Etsy.)
Tradenames of cultured pearls are Akoya, white or golden South sea, and black Tahitian.
Akoya pearls are the specialty of Japanese pearl farms. Because Akoya pearls are a high-quality pearl, you'll find them set with gold posts and clasps, and you'll find they are well matched for size, shape, and color. You'll also find few blemishes and a deep, beautiful luster. The Akoya looks very similar to the Freshwater pearl. But on average, Akoya pearls are larger, smoother, rounder, and more lustrous than Freshwater pearls. A wire Wrap necklace of Iolite Moonstone and cultured Blue Akoya Pearls shown to the left is from RohrJewelers on Etsy.
South Sea pearls are the color of their host Pinctada maxima oyster – and can be white, silver, pink, gold, cream, and any combination of these basic colors, including overtones of the various colors of the rainbow displayed in the pearl nacre of the oyster shell itself. South Sea pearls are the largest and rarest of the cultured pearls – making them the most valuable. They are prized for their exquisitely beautiful luster. The beautiful golden South Sea Pearl and diamond earrings to the right are from OrMana on Etsy.
Tahitian pearls, frequently referred to as black pearls, are highly valued because of their rarity; the culturing process for them dictates a smaller volume output and they can never be mass-produced because, in common with most sea pearls, the oyster can only be nucleated with one pearl at a time, while freshwater mussels are capable of multiple pearl implants. Tahitian pearls are interestingly not exclusively from Tahiti – they’re grown in several of the islands of French Polynesia, including Tahiti. Their typical sizes range from 8mm to 16mm. These naturally colored pearls are collectively called black pearls, but their colors include shades of green, purple, aubergine, blue, grey, silver or peacock (a mix of several shades, like a peacock's feather). Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced naturally black pearls, and black pearl oysters rarely produced any natural pearls at all. (To the right above is a Tahitian pearl ring from LusterWear on Etsy.)
Saltwater pearls include the Akoya cultured pearls grown in Japanese and Chinese waters. They range in size from 2mm (tiny) to 10mm (rare) and are usually white or cream in color and round in shape. Australia, Indonesia, and the Philippines produce the South Sea pearl – the largest of all the pearls. They range in size from 9mm to 20mm and can be naturally white, cream, or golden in color. On the left above is a saltwater Baroque Pearl necklace from TANGRA2009 on Etsy.
These pearls are grown in freshwater lakes, rivers, and ponds, predominately in China. Although many are white and resemble the akoya cultured pearls in shape and size, they can also be produced in various shapes and in an array of pastel colors. Many freshwater pearls don’t have a bead nucleus — only a piece of tissue — resulting in a pearl with thicker nacre than the akoya. To the left is necklace from GinnyTaylorDesigns on Etsy, featuring London Blue Topaz with Peacock Freshwater Pearls.
Imitation pearls are usually a coated glass bead. Most have a high luster, but not the depth of luster seen on high quality cultured pearls. You can easily separate an imitation from a cultured or natural pearl. It can be a challenge, though, to determine if the pearl is cultured or natural. And, many pearls undergo treatments to either enhance their luster or alter their color. Since this treatment affects their value, you will want to obtain the educated advice of a top jeweler, such as the certified gemologists of the American Gem Society.
For those of you who want to make or wear pearl jewelry, we hope this introduction has been helpful. If you'd like to know more about working with pearls, you might check out this tutorial on hand-knotting from Fire Mountain Gems. (One reason to knot pearls is to keep all of them from falling off the strand if it breaks; it's also done to keep them from touching, which can result in chipping the outer surface.)
I highly recommend the Tucson Gem and Mineral Show for finding all sorts of incredible pearls. I'll never forget the football-field-sized building full of tables piled high with so many pearls -- it was truly mind-boggling (and wonderful). If you enjoyed this post, you might also like Rocks to Gems and My Addiction to Gems (In This Case, Emeralds)...