There are essentially three types of pearls: natural, cultured and imitation.
Natural Pearls form when an irritant - usually a parasite and not the proverbial grain of sand - works its way into an oyster, mussel, or clam. As a defence mechanism, a fluid is used to coat the irritant. Layer upon layer of this coating, called 'nacre', is deposited until a lustrous pearl is formed.
A cultured pearl undergoes the same process. The only difference is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl. These 'seeds' or 'nuclei' are most often formed from mussel shells. Quality cultured pearls require a sufficient amount of time - generally at least 3 years - for a thick layer of nacre to be deposited, resulting in a beautiful, gem-quality pearl. Lower-quality pearls have often been 'rushed' out of the oyster too quickly (sometimes a year or less) and have a too-thin coat of nacre.
Pearls can come from either salt or freshwater sources. Historically, saltwater pearls were rounder and had a better nacre than freshwater pearls, while freshwater pearls tended to be very irregular in shape, with a puffed rice appearance the most prevalent. However, improvements in freshwater pearl farming techniques have narrowed that gap, with freshwater pearls now exhibiting great roundness and deep lustre.
The culturing process usually takes several years. Mussels must reach a mature age, which can take up to 3 years, and only then can be implanted or naturally receive an irritant. Once the irritant is in place, it can take up to another 3 years for the pearl to reach its full size and nacre thickness. Of the pearls produced, only approximately 5% are of sufficient true gem-quality for top jewellery makers, yet a pearl farmer can figure on spending over $100 for every oyster that is farmed, whether a gem-quality pearl is produced or not.
Imitation pearls are a different story altogether. In most cases, a glass bead is dipped into a solution made from fish scales. This coating is thin and may eventually wear off. One can usually tell an imitation by rubbing it across the teeth: Fake pearls glide across your teeth, while the layers of nacre on real pearls feel gritty. The Island of Mallorca is known for its imitation pearl industry, and the term "Mallorca Pearls" or "Majorica Pearls" is frequently (though inaccurately) used to describe these pearl simulants.
Over the course of fifty years, Australian pearlers have unlocked the secret of producing superior pearls that do not require processing or enhancement to reveal their beauty.
Culturing South Sea pearls begins with the search for the prized Pinctada maxima pearl oyster. Australia is in the fortunate and unique position of having rich wild pearl beds that allow the majority of oysters used for pearl cultivation to be collected from the wild, rather than grown in hatcheries.
Teams of divers search the sea floor at depths of up to 35m
to collect the wild oysters by hand. This is an environmentally friendly form of fishing resulting in no wasteful by-catch or damage to the ocean floor.
In accordance with Australian government regulations, only a specific number of wild oysters of the appropriate size are collected, ensuring the long-term sustainability of the pearl fishery.
The selected oysters are collected at an area of the seabed known as a ‘nursery’ to await the seeding operation. On very rare occasions a wild oyster already holds one of nature’s most prized gems – a natural pearl.
The seeding process is a meticulous and highly specialised operation.
On board state-of-the-art pearling vessels, the Pinctada maxima oysters are held in tanks of circulating seawater. A nucleus (in this case a small polished sphere of Mississippi freshwater clam shell) is implanted into each oyster by a skilled technician.
Over time, a pearl forms as the oyster surrounds the nucleus with thousands of layers of nacre. Australian South Sea pearls are husbanded for at least two years to ensure the growth of thick layers of nacre that are necessary to give a pearl radiant natural lustre.
Maintaining the oyster in prime health is the key to producing pearls of high quality. This would be impossible but for the location of the pearl farms in the unpolluted waters of north-western Australia, remote from centres of population.
For the duration of the husbandry period, each oyster is carefully cleaned every
few weeks to remove marine growth that would otherwise compromise its health.
When harvest time arrives the oysters are raised from the ocean and transported to the harvest vessel. There, technicians delicately open the oyster and remove its creation. Only then is the quality of the pearl revealed. Oysters that produce a pearl of exceptional quality may be seeded again for a further harvest.
5. PEARL GRADING
Grading is an exacting and time-consuming process carried out by experts with years of experience. The range of combinations of size, colour, lustre, shape and skin quality is vast. Without this stringent grading process, it would be impossible to ensure consistency when pearls are matched for pairs and strands.