Luster is the result of the way light shines off the surface, and just under the surface of a pearl. It gives a pearl a radiant, mirror-like quality and is one of the greatest factors in determining its value. It can also be seen in the sharpness of reflections on the pearl’s surface. A clear and sharp reflection indicates good luster, while a dim or blurred reflection denotes poor luster. The Gemological Institute of America (GIA), a respected institution when it comes to diamond and gemstone grading, uses a scale of Excellent to Poor to grade pearl luster.
Nacre forms the layers of a pearl around the nucleus. Whether the nucleus is a natural irritant (natural pearl) or a man-made irritant (cultured pearl), nacre forms around the nucleus to protect the mollusk and creates a pearl in the process. Pearl grading reports from the GIA have the option to include the nacre thickness of a pearl, which is important in order to assess the durability of a pearl.
The surface quality of a pearl relates to how “clean” the surface is. The GIA grades pearl surface quality by looking for the presence, size, and number of blemishes. They use a grading scale for pearl surface quality that includes Clean, Lightly Spotted, Moderately Spotted, or Heavily Spotted.
Cultured pearls are pearls that have been created with human intervention. They are still created in an oyster through the same process as natural pearls, but the irritant that results in a pearl is placed in the oyster by humans. Cultured pearls are identical to natural pearls except for how the origin irritant entered the pearl.
The invention of cultured pearls, often credited to Kokichi Masimoto, helped pearls enter the mainstream jewelry industry rather than remaining isolated to the nobility and upper classes. “Cultured” refers to the method of creation more than the type of pearl. Any type of pearl can be cultured, i.e., cultured freshwater pearls, cultured akoya pearls, etc.
Freshwater pearls are pearls that grow in freshwater bivalve mussels that live in lakes, riverbeds, and creeks. Mussels that produce freshwater pearls are capable of producing up to 50 pearls at a time. The freshwater pearl industry is overwhelmingly dominated by Chinese production, with other notable producers being Japan and the United States.
Freshwater pearls are the most common type of pearl, and they also provide the greatest diversity in terms of color, shape, and size compared to other pearls. Perfectly round freshwater pearls are very rare, and you will often see freshwater pearl jewelry highlighting unique shapes such as potato or baroque. Freshwater pearls are known for their distinctive texture and warm luster.
Akoya pearls originate from the saltwater mollusk known as Pinctada Fucata, which is found in the Indo-Pacific area. Akoya pearls were the first to be cultured in 1893 and began to be mass-produced in 1916. The Akoya pearl oysters are typically only nucleated with one or two beads at a time, and can take 18 months to 2 years to develop pearls.
According to the GIA (Gemological Institute of America), Akoya pearls are what people generally think of when they think of a classic pearl. They are often very round (though they can be found in other shapes) and have a sharp luster. While common colors include white or creamy white, they are also found in grey-blue and, rarely, blue and gold hues.
One of the things that stands out about akoya pearls is their overtones. Overtones are the secondary colors visible in a pearl and are distinct from its body color. A popular overtone is rose or blush pink, and other overtones include cream, aquamarine, silver, green, gold, and violet. Vietnamese Akoyas typically have brighter and more vivid body color and overtones, as compared to Japanese Akoya pearls.
Tahitian pearls are the alluring and mysterious dark pearls that are commonly referred to as black pearls. These are the only true “black pearls,” as all other pearl types would be color-treated to achieve a black color. Natural Tahitian pearls are extremely rare, so most Tahitian pearls on the market are cultured. Mikimoto attempted to culture Tahitian pearls after his initial success, but it wasn’t until 1972 that the first successful farming of Tahitian pearls occurred in French Polynesia by Jacques and Hubert Rosenthal.
Tahitian pearls are cultivated using the Pinctada margaritifera oyster, which is native to the South Pacific, including French Polynesia, Micronesia, and the Cook Islands. Although sometimes referred to as “black pearls,” Tahitian pearls can have body colors of grey, charcoal, and black, and, rarely, silvery white or gold.
The range of overtones possible for Tahitian pearls is quite extensive, including cherry, dark pink, green, green-cherry, yellow, gold, brown, pistachio, blue, turquoise, aubergine, and peacock.
Beyond their unique colors, Tahitian pearls are also known for their large size, being some of the largest cultured pearls in the world, with an average size of 9-13MM.
South Sea pearls are cultivated in the Pinctada maxima oyster found natively in the South China Sea and the Indian Ocean. They are commonly found in white or gold. White South Sea pearls are farmed in northern Australia, Indonesia, the Philippines, and Myanmar. They can be found in body colors of white, blue-white, silvery white, and ivory white, with possible overtones of silver, blue, aquamarine, ivory, cream, and pink or blush rose.
Golden South Sea pearls are farmed in Indonesia, Myanmar, Australia, and the Philippines. They can be found with a range of body colors, including pale yellow, light gold, champagne, medium gold, and deep gold, with possible overtones of gold, bronze, and green.
Due to recent innovations in pearl culturing, Golden South Sea pearls were harvested in Myanmar that displayed rainbow overtones, similar to those of Tahitian pearls. These extremely rare pearls are known as Rainbow Gold South Sea pearls. A Pinctada maxima oyster is usually allowed to grow for about 3.5-4 years before being nucleated, after which it takes about 2 to 3 years for an oyster to produce a single pearl. For this reason, South Sea pearls are somewhat rarer and more expensive than other types of cultured pearls.
South Sea pearls can be found in a variety of shapes, including round, off-round, oval, button, drop, baroque, and circlé. They are one of the largest cultured pearls in the world, averaging 9-14 mm in size, though some have been found at 20 mm, and baroque South Sea pearls have been found as large as 28 mm.
Mabe pearls can be produced by a variety of mollusks, and they are distinct for their cultivation process and shape. Also known as “blister pearls” and “half pearls,” mabe pearls grow against the edge of the mollusk shell instead of freely within the soft tissue like other pearl types. They usually require 2-3 years for production, are lighter than other pearl types, and can easily reach larger sizes, with an average size of 10-25 mm.
The most common mollusks where mabe pearls are produced include the Ptera penguin (Winged Oyster), Ptera sterna (Rainbow-Lip Oyster), Pinctada maxima (South Sea Oyster), and Haliotis iris (Abalone mollusk). Each mollusk can produce distinct mabe pearls in terms of their color, size, and shape.
Mabe pearls from the Winged oyster make up the majority (about 75%) of production and often contain a silvery-grey body with overtones of pink, green, violet, and blue. They are native to the western and central Indo-Pacific region.
From the Rainbow-Lip oyster, mabe pearl production is rare, and these specific mabe pearls are sometimes referred to as “Sea of Cortez” pearls. They are often found with a medium grey body color and with overtones of pink, green, violet, and blue. They are found in the shallow waters of the tropical and subtropical Pacific coast of America, with a range extending from Baja, California, to the shores of central Peru.
South Sea oysters can produce mabe pearls in sizes of 10 MM or greater, and often have body colors of silvery-white or golden, depending on the type of oyster. South Sea mabe pearls are typically created at the end of an oyster’s life cycle after they have already produced round South Sea pearls. They are native to the Indo-Pacific region, ranging from Myanmar to the Solomon Islands.
Mabe pearls from Abalone mollusks, also called Blackfoot Pāua and Rainbow Abalone,
are especially distinct with a body color of intense blue and overtones of pink, green, and gold. They can be found in a variety of shapes, including round, drop, and oval, with sizes averaging 9-13 MM and able to reach up to 20 MM. These mollusks are endemic to New Zealand and are typically found in shallow waters.
Baroque pearls refer to a shape rather than to a type of pearl. Common pearl types, including freshwater, Akoya, Tahitian, and South Sea, can be found in a baroque shape. Before the innovation of cultured pearls, baroque pearls were much more common and considered quite valuable. As Mikimoto emphasized the production of “perfect” round pearls, baroque pearls began to decline in popularity and were seen by some as “inferior.”
Baroque pearls are organic in shape; they do not adhere to a round symmetry. Because of this, baroque pearls are completely unique, like snowflakes or fingerprints. They can have smooth surfaces with free-form shapes, grooves or circles, knobby bumps or tips, or some combination of these traits.
Due to their uneven surface, baroque pearls are known for their exceptional luster and iridescence. This is because there are more angles at which light can hit the surface of a baroque pearl, creating increased visual interest. While baroque pearls declined in popularity due to the increased access to round and symmetrical pearls on the market, they are again gaining popularity due to their unique and beautiful qualities.
