All About Pearls

A brief history of pearls

Humans have considered pearls to be a wonderful treasure for thousands of years. The earliest evidence that humans valued pearls is from burial sites in the Persian Gulf region from as early as 4000 B.C. During the first century B.C., Roman women encrusted their clothing and even their furniture with pearls. In addition, the ancient Chinese, Egyptians, Greeks and Native Americans have all made elaborate use of pearls for decoration and adornment for both men and women.

The Chinese were probably the first to culture pearls beginning in the fifth century A.D. by inserting tiny Buddha figures that were turned into blister pearls (attached to the oyster shell), but culturing did not become a commercial process until the early 20th century.

In Europe in the Middle Ages, only the nobility were allowed to wear pearls. Royal freshwater pearl beds were heavily guarded and poachers were sometimes put to death. After Columbus discovered plentiful and exceptionally beautiful pearls in the Caribbean and Central America, the New World became known as the Land of Pearls. As pearls from the Americas and other trade routes made the gems more plentiful than ever, both the European royalty and the upper classes adorned themselves in elaborate pearl jewelry.

While pearl beads were worn in many Native American cultures, mother of pearl was generally more highly regarded by native North Americans. The mother of pearl shells of the North American pearl mussels are so large and thick that the freshwater pearl beds of the Ohio, Tennessee and Mississippi River basins eventually became the center of the button industry from the mid 19th century through the mid 20th century. Their shells are still used as the nuclei for most cultured pearls today.

In the early 1900s, several researchers in Japan simultaneously discovered effective ways to culture pearls. Kokichi Mikimoto, a talented and driven entrepreneur, was one of them, although he initially produced only mabe pearls. It took him more than a decade to develop a method for consistently culturing the round Akoya pearls that immediately come to mind with the name Mikimoto. He also used his considerable marketing and business skills to overcome the idea that cultured pearls were "fakes" compared to natural pearls, so that today's consumers consider cultured pearls to be gemstones of exceptional beauty and value.

Cultured versus natural pearls

Only certain types of oysters and mussels create gemlike pearls. The oyster you typically eat in a restaurant isn't one of them, although pearl oysters are eaten in other cultures.

Naturally occurring gem-quality pearls are quite rare, and perfectly round pearls are even rarer. Natural pearls are formed in the same way that cultured pearls are: an irritant gets stuck in the wrong spot in a pearl oyster (saltwater) or mussel (freshwater) and the oyster secretes nacre, which is the same substance as mother of pearl, to coat it. Contrary to popular belief, a grain of sand would generally not be a significant enough irritant to an oyster to create a pearl. Parasites and food particles are far more common but somewhat less romantic natural irritants.

Cultured saltwater pearls are created when a human inserts a nucleus (typically a mother of pearl bead) along with a graft of tissue from another oyster into a special spot in the oyster, waits a few months or even years, then removes the resulting pearl. Cultured freshwater pearls are usually created using only a tissue graft, because the mantle (the part of the mollusk that secretes nacre) of pearl mussels is generally too thin to successfully use a bead nucleus.

Differences between freshwater and saltwater pearls

Saltwater pearls are formed by marine mollusks, including oysters, conchs and abalone. There are even a couple of marine snails that form gem-quality pearls, but the vast majority of commercial pearls are from oysters and other bivalves (mollusks with two shells). In order to ensure a more perfectly round pearl, only a small section of tissue near a pearl oyster's reproductive organs is implanted with a nucleus, so oysters typically only make one or two pearls at a time. However, many of them can be reseeded up to four times and as they grow larger, they can accommodate larger nuclei and therefore create larger pearls over time.

Mussels living in the sand or mud of lakes, rivers and streams form freshwater pearls. Instead of using a mother of pearl nucleus, just a piece of mantle tissue from another mussel is implanted in the mussel. Because freshwater pearls are created without a nucleus, they are made entirely of nacre. Freshwater pearl mussels can create dozens of pearls at a time because their entire mantle tissue on both sides can be nucleated. They usually cannot be reseeded, however.

Cultured freshwater pearls come in a wider variety of shapes and colors than cultured saltwater pearls do, and they are often more iridescent than saltwater pearls. While freshwater pearls are almost never round, Chinese manufacturers have recently been inserting nuclei experimentally to create round freshwater pearls.

The unique appearance of pearls

Pearls consist of concentric layers of calcium carbonate, in the form of the crystal aragonite, cemented together by small amounts of conchiolin, a protein that acts as mortar. The combination of aragonite and conchiolin is called nacre, and it is the same substance as the mother of pearl found on the mollusk's shell. Nacre has two qualities that make pearls special among gemstones: luster and iridescent orient.

Luster describes the way pearls seem to glow from within. It's based on the depth of reflection due to the layering of the aragonite crystal, so as a general rule, the thicker the nacre, the higher a pearl's luster will be.

Iridescent orient is the bubble-like play of colors across the surface of a pearl. It's created by the particular alignment of the crystals so that they reflect off each other and create prisms.

The color of pearls

Pearls come in a variety of lovely but relatively limited shades naturally. The color of a pearl is controlled by the species of mollusk and environmental factors—primarily the water's composition. Freshwater pearls come in white, pink, peach, mauve, cream, white and gray, among others. Saltwater pearls may be white, cream, yellow, pink, black, silver or gray.

Pearls have three primary color characteristics:

Bodycolor: the underlying color of the pearl, such as white, gold, gray, etc. All pearls have a bodycolor.
Overtone: a translucent "coating" of color. A silver pearl may have a blue overtone or a green overtone, for example. Not all pearls have an overtone.
Iridescent orient: the variable play of colors across the surface of the pearl like a rainbow. Not all pearls have iridescent orient.

Because pearls naturally come in a somewhat limited selection of colors, humans have invented numerous ways to alter their color, including dying, bleaching, chemically treating and irradiating. This means that pearls can be found in nearly every shade imaginable.

Pearl shapes

Today pearls come in an ever-growing variety of shapes. While there is no standard definition for many of these shapes, some of the most common include:

Round: Perfectly spherical, or very nearly so. These are primarily saltwater pearls, although the Chinese have recently succeeded in creating round freshwater pearls.
Semi-round: Almost round, as the name implies. These are primarily saltwater pearls.
Symmetrical: Any symmetrical non-spherical shape, including teardrops or pear shapes. This term has traditionally been applied to saltwater pearls.
Baroque: Nearly any non-round shape. This term has traditionally been applied to irregularly shaped saltwater pearls.
Stick: Long and thin with many irregularities.
Rice: Small ovals drilled lengthwise.
Potato: Often lumpy, these are typically rounder than rice pearls and may be drilled either lengthwise or widthwise.
Nugget: Typically a little more square or pebble shaped than rice or potato pearls, with a flat side.
Coin: Large, circular and flat, often about the size of a dime, with the hole drilled end-to-end. Coin pearls, unlike most freshwater pearls, are created using a bead nucleus.
Keishi: Sometimes called "cornflake" pearls, these are flat and highly irregular. Keishi pearls are formed when an oyster manages to expel a bead nucleus, but continues to make a pearl.
Drop: Teardrop, pear or even peanut shapes, drilled either lengthwise, or widthwise at the narrowest end.
Button: Rondelle shaped, often with a flat side, and drilled through the "hub" of the wheel.

Designing with pearls

Because pearl beads come in so many shapes and colors today, the options for jewelry designers are virtually limitless. While round white pearls have traditionally been knotted on silk cord to form single or multi-strand necklaces, today's designers are stringing every color and shape of pearl bead on contemporary threading materials, working them into wire designs, and combining them with every type of bead, including glass, metal and gemstones. At Pearl Bead Sale, we offer a wide range of pearls from the attractive yet affordable to the truly exceptional, and we strive to give designers the information and tools they need to create beautiful pearl jewelry.