This article was originally found in the Florida Society of Goldsmith Newsletter, Spring 2014. Written by Brenda Smith. Click on the image to obtain the PDF, and read the article complete with images.
Pearls are considered a gemstone and have always fascinated me. However, I find myself in good company. Pearls have been collected, cherished, highly valued and used for adornment since the beginning of time. Once only available to royalty and the wealthy, pearls can be enjoyed by the average consumer worldwide since the development of cultured pearls in 1908 by Mikimoto, the Japanese son of a noodle maker.
A cultured cultured pearl is the process of inserting a nucleus surgically into the mollusk. The mollusk then coats this irritating nucleus with layers of nacre, which produces the iridescence of the pearl. The mantle’s epithelial cells form a sac, known as the cultured pearl sac, which secretes a crystalline substance called nacre, the same substance which makes up the interior of a mollusk’s shell, which builds up in layers around the irritant, forming a pearl. This nucleus is typically spherical and is created from ground and formed mollusks harvested from the Mississippi River basin, then shipped worldwide. A small portion of a donor mollusk mantle tissue is inserted surgically along with the nucleus into the host mollusk.
Before pearls were cultured, it was a game of chance. Pearls were formed after a parasite or foreign substance invades the soft mantle tissue of the mollusk. To fi nd enough matched pearls, in size, shape, surface quality, color, and luster was very rare. These pearls would form entirely by nature and were solid nacre. These pearls are called “natural” pearls. With the advent of culturing the pearl, farms were developed to control quantities and these variables. These pearls are called “natural color” pearls unless they are dyed. In which case, they are neither naturally created nor naturally colored but are still genuine pearls.
Whether wild or cultured, gem quality pearls are almost always nacreous and iridescent, as is the interior of the shell which produces them. Almost all species of shelled mollusks are capable of producing pearls of lesser shine or spherical shape. Although these may be legitimately referred to as pearls, most of them have no value, except as curiosities.
Basic Cultured Pearl Types
Freshwater pearls are best know for their wide range of shapes, sizes, colors, and attractive prices. They were fi rst produced around 1914 and are produced by the Hyriopsis cumingi mussels, which live in the lakes and rivers mostly in remote areas of China. Serious Chinese production started in the 1970s.
The mussels are nucleated with tiny, rectangular slices of mantle tissue, resulting in pearls made of solid nacre but only about 3% are round. Roughly the size of a human hand, these prolific mussels are able to produce up to 50+ pearls at a time, densely clustered on each shell. Due to pollution, however, the Chinese cultured pearl production has been down in recent years. And close to home, the state of Tennessee is also a source of freshwater pearls. A few small farms are open for tours.
Freshwater pearls offer attractive prices for several reasons.
- One mussel can produce 50+ per harvest vs. one cultured pearl in saltwater.
- They are nucleated with mantle tissue, which is much less labor intensive.
- They can be grown in much harsher water than saltwater pearls.
- Harvesting is typically two years vs. four years for saltwater pearls.
Saltwater Akoya Pearls
Akoya pearls are treasured for their true roundness and reflective shine. They come from a small Japanese oyster that produces only one cultured pearl at a time. The salt water Pinctada fucata oyster lives along the coasts of Japan and China. A nucleated bead is surgically implanted in the body of the oyster, which coats it layer upon layer of beautiful nacre. These relatively small pearls range in size from 2-10mm. Akoyas larger than 8mm are quite rare and valuable. Akoyas come in rose, silver/white, cream, gold, and blue/ gray colors.
Tahitian and Black South Sea Pearls
Tahitian pearls are the only pearls in the world that are naturally black. The Pinctada margaritifera oyster, native to Tahiti and the French Polynesian Islands, produces rare, exotic, and luxurious, Black South Sea pearls. These salt water oysters can grow as large as a dinner plate, resulting in pearls that range from 8-18mm in size. Tahitian pearls come in an array of beautiful colors, from silver to deep black, with shades of green, blue, and pink.
White South Sea and Golden South Sea Pearls
White South Sea and Golden South Sea pearls are treasured for their luxurious size and brilliant satin luster. These valuable pearls are produced by the silver-lipped oyster, Pinctada maxima, along the coast of Australia, Indonesia, and the Philippines. As the rarest pearls on earth, a single strand of these magnificent gems can take many years’ of harvests to assemble, as each cultured pearl must be painstakingly matched for size, roundness, color, and quality.