Pearls, natural or cultured, are formed when a mollusk produces layers of nacre around some type of irritant implanted in the shell. In natural pearls, the irritant may be another organism from the water. In cultured pearls, a mother-of-pearl bead or a piece of tissue is inserted into the mollusk to start the process.
For both, the quality of the nacre dictates the quality of the luster, or iridescence of the pearl, which is very important to its beauty and value. The surface of the pearl should be smooth and free of marks while the overall shape could be round, oval, or pear-shaped. Irregular looking pearls are called baroque pearls.
Traditional types of cultured pearls are Akoya pearls, fresh water pearls, Tahitian pearls, and South Sea pearls. Akoya pearls are cultured in Japan, perfectly round and white, with a high luster and max.size of 8-10 mm. Fresh water pearls, from fresh water mussels, are raised mainly in China and originally marketed as more affordable and lesser quality. Akoya now come in all sizes and shapes. Tahitian pearls produced in French Polynesia, are rare and vibrant, with many beautiful shades of grey, green, and other colors. They are round and up to 15mm in size. South sea pearls are 
cultured in North Australia, Indonesia, and South East Asia. They are white or gold with a satin luster. The largest sizes are from 15-20 mm.
Then there are cultured pearls formed on the inside of an oyster shell called Mabe pearls. When they include surrounding part of the shell they become Blister pearls, favored by designers because of their sculptural forms. Very unusual Mabe pearls are cultured in Abalone, Haliotis. The rarest pearls are pale to hot pink pearls created by Conch, Strombus Gigas. Their surface is porcelain like, instead of iridescent. Another type of pearl is a Keshi pearl, which is created by mollusk without an insert, it is a formation of pure nacre always very irregular in shape and in variety of sizes.
The production of a cultured pearl is complex and requires a thriving marine ecosystem, important knowledge and skill, and many years of patience. In Australia, pearl farmers can collect wild adult oysters under a strict quota system. Otherwise, young oysters can either be collected as spat from the wild during natural spawning seasons or be artificially spawned in hatcheries. The oyster can be seeded two to three years after its birth by implantation of a nucleus which is gradually covered with nacre or mother-of-pearl by the mollusk. This period of growth of
a cultured pearl takes a further one to two years, depending on a range of factors: the time from the birth of the oyster to the harvest of the first pearl is about three to four years.
Not all oysters will survive the implantation process, and not all oysters will produce a beautiful pearl. Estimates suggest that 95 percent of a pearl farm’s income comes from 2 percent of its pearls. The skills of the seeding and implanting technicians play one important role. Environmental deterioration or sudden ecological changes will also affect the oyster and hamper its potential for producing a high-quality pearl, as pearl oysters are remarkably sensitive organisms.
Before the invention of cultured pearl farming, pearls could only be found in the wild. Thousands of oysters needed to be opened to find just a few pearls, and for centuries, the world’s pearl oysters and mussels were fished in large quantities. This led to the over-exploitation of these mollusk stocks.
One such example was the pearl rush that happened around the Mississippi river during the 19th century. When pearls were found in the Upper Mississippi River, it led to a large treasure hunt. Millions of mussels were killed in the process until there were almost none left. Oysters weren’t valuable only for the pearls but also for the shells which were used to make buttons. In the early 20th century, when Mikimoto discovered a way to produce cultured pearls the large-scale fishing of wild pearls became less and less practiced.
For this article I choose to show images of variety of pearls: Mabe, Blister, Freshwater Coin and Stick, and stunning Round pearls, all used to create many different designs of necklaces or brooches.
Born in Croatia, Sylvia Gottwald studied fine art and design in Italy and Canada prior to earning her Masters of Architecture from Harvard University and completing her post-graduate in City Planning at MIT. In 2000, following her long, successful career practicing architecture and urban planning locally and internationally, she turned her attention and efforts to the gems of the oceans.Ms. Gottwald transforms the natural beauty and iridescence of nacre/mother-of-pearl and pearls into contemporary wearable art. Her avant-garde designs integrate nacre with precious metals, semi-precious gems, and edgy modernmaterials such as rubber and steel. Her interest in nacre is not only it’s inherent beauty, but also the importance of oysters to our marine ecosystems. The pearly oysters filter polluting nitrogen and plankton, protecting the oceans, and adding to the sustainability of life on our planet. In addition to their precious nacreous shell, they create a mysterious gem- the pearl- the only gem created by a living organism. Ms. Gottwald’s growing list of published work includes the covers of European Vogue, Elle Decor, Ornament, Home & Design, exhibited at the Musée des Arts décoratifs, Palais du Louvre (Paris); Musée de la Nacre (Paris/Meru); Museum of Modern Art (New York City); Museum of Contemporary Art Kampa (Prague); Museum of Women in the Arts (Washington, DC); and the International Museum. Photo: SYLVIA GOTTWALD, in Dubrovnik, Croatia, 2012. Photograph by Domagoj Blazevic. of Applied Arts (Turin).