Natural vs Cultured Pearls
Prior to the 20th century, pearls were extremely rare and expensive gems, affordable by only the most wealthy. Back then, all pearls were natural pearls, formed in oysters in the wild without any human intervention. These oysters were hunted by pearl divers - a very dangerous job and extremely labor-intensive besides. For each ton of oysters that were gathered only a handful would yield a pearl!
In early 1900's, a team of Japanese scientists invented the process of pearl culture. Patented in 1916, the first commercial crop of farmed cultured pearls was harvested in the late 1920's, opening the door to today's multi-million dollar pearl farming industry.
What's the difference between Natural and Cultured Pearls?
Pearl oysters secrete a protective substance composed of platelets of aragonite (calcium carbonate) which is called Nacre. The platelet formation is what gives nacre its characteristic irridescent qualities. Nacre makes up the smooth "mother of pearl" lining inside the oyster's shell - its purpose is to coat and protect the animal from harmful agents which invade the shell. Pearls are produced when something irritates the inside of the oyster, causing an over-production and build-up of nacre - a process which continues throughout the oyster's life.
In natural pearls, the irritant is usually a parasite, virus or a small foreign body like a grain of sand. As a result, natural pearls are almost entirely composed of nacre and rarely have a regular or round shape.
Cultured pearls are farmed on pearl farms. Pearls are created by seeding the oyster with pre-formed beads known as shell beads. These beads can be different shapes, such as round or teardrop - the resulting pearl will have the same shape as the shell bead nucleus.
Cultured pearls produced in this manner have a thinner coating of nacre surrounding the implanted bead.
A slightly different method, called the mantle tissue insertion method, is used to produce cultured freshwater pearls. In this process, small pieces of mantle tissue form a donor oyster are inserted into the oyster. The pearl, which is composed entirely of nacre, forms around this foreign tissue.
How Do You Tell a Natural Pearl from a Cultured Pearl?
The best way to verify if a pearl is a natural pearl is to xray it in order to see what's at its center. An xray will also reveal growth rings in the nacre or a natural pearl.
Because of their rarity, nearly all pearl jewelry seen today is made from cultured pearls. Natural pearls can be found in antique pearl jewelry that dates from the 19th century or earlier.
Modern pearl farms and the advent of cultured pearls have greatly increased availability of pearl jewelry and helped put the prices of these beautiful gems within reach of the average consumer!
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