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Australia is the world’s major producer of white South Sea pearls, for during the 1998 season the tropical waters off northern Australia yielded ~ 60 per cent of total world production of these much desired and very valuable bead-nucleated cultured pearls.
White South Sea pearls are large (>10 mm diameter) rounded, lustrous, white, silvery, cream, or golden pearls that are cultivated by man in the gold- and silver-lipped pearl oyster (Pinctada maxima) that is indigenous to the off-shore waters of northern Australia. Other white South Sea pearls produced by the Australian pearling industry include ‘accidental’ whole baroque keshi pearls, and cultured bead nucleated half pearls that are commonly termed mabés.
The white South Sea pearl is a comparative newcomer to Australia’s pearling industry, for the history of this primary industry stretches back for well over a century to the time when Australia was one of the major supplier of natural pearls to European and American markets. |
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Typical Work Schedule for an Australian Pearl Farm
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January
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Prepare for wild shell collection, organise dive crews, fishing gear,
paperwork and licence fees. |
February
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Fishing for 20,000 wild shell begins, linked to tide charts.
(Note: Tides in the area can vary by 10 m per day.) |
March
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Collected shell is ‘dumped’ on the seabed on site owned or leased by the company and allowed to rest. Maintenance of dumped shells, turning and cleaning them. X-ray shells seeded last year to check if implanted nuclei have been rejected. Oysters that reject nuclei are usually re-seeded.
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| April |
Water temperature begins to drop as winter approaches, rest period for the shells.
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May
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Ongoing farm work, turning and cleaning previous two year’s seeded oysters kept suspended in wire panels in the water column. |
| June |
Prepare for operating on oysters to implant nuclei. (Note: Some technicians may come from overseas, and some companies have boats fitted as mobile laboratories so seeding can be done on the pearling grounds.) Seeding and harvesting begin.
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July
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Normal operating time for pearls, seeding new oyster, re-seeding those which have rejected nuclei. Oysters that produce acceptable pearls are also re-seeded. |
August
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Harvest of previous year's seeded shell continues, then a two-month turning program follows operations. The oysters are turned over to encourage production of round pearls. |
September
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Turning operated shell.
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October
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Turning, cleaning and change of areas. |
November
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Transportation of operated shell to grow-out areas. |
| December |
Dump and clean gear. |
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 Pearls are harvested in the cooler winter months, after about two years of cultivation. This time is deliberately chosen, for in the winter months nacre secretion is slower, more uniform, and the nacre has peak lustre. Also the lower temperatures seem to reduce stress and consequent mortality in the shells.
At harvest the pearls are categorised into saleable bead nucleated pearls, rejects, and keshis. It is important to remember that today there is a growing market for designer-friendly natural pearl look-alike baroque all-nacre Australian keshis.
Presently, the overall mortality rate for seeded shell, over the two-year cultivation period, is a mere 5 per cent. When to this mortality is added the 4 per cent of molluscs that must be sacrificed to yield the siabou (nacre-secreting graft ) tissue, a 3-5 per cent post operation mortality, and a 20 per cent rate of nuclei rejection; this leaves approximately 66 per cent of implanted shell healthy enough to form pearls.
The yield of good quality pearls usually determines that about 60 per cent of shell that contained a saleable pearl will be reseeded - this time with a nucleus the same size as that of the pearl that was removed. The reason for less shell being reseeded, irrespective of producing a saleable first crop pearl, is simply that as the reseeded pearl is likely to be of lesser quality than the original pearl only shells capable of producing a good quality first crop pearls are reseeded. The shell is then cultivated for a further two years, with about 40 per cent of implanted shells that remain following mortality and nucleus rejection being suitable for implantation with a third nucleus and so being capable of yielding 17-19 mm pearls. Indeed, up to four pearls have been produced from a single shell before it was considered unsuitable for round pearl production.
Typical harvest results claimed for West Australian white South Sea pearl production include: first extraction, ~85 per cent saleable with an average weight of ~16.5 ct; second extraction, ~65 per cent saleable with an average weight of between 21.5 and 23 ct; while the third extraction produces a variable yield of large size pearls.
Each day’s harvest is initially sorted and graded into categories of colour, size, and shape by shipboard implantation technicians. The reason is quite simple, for the financial reward of these technicians often is tied to the productivity of his or her implanted shells.
The pearls are then transported to the company’s headquarters, where they are carefully cleaned of residual mucus or salt, before the better quality pearls are gently tumbled with a mild abrasive, such as cooking salt, to remove any adherent organic material (dried mucus) and thus optimise the lustre and orient of the pearls. Lower grade pearls are only tumbled in finely ground pumice to enhance smoothness; for South Sea pearls are not colour-enhanced in any way by bleaching and/or dyeing.
Following cleaning, the pearls are sized, classified, and graded ready for sale to world markets. |
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