Bulletin 5 - July 1978: The Production of Pearls

The Production of Pearls

(Professor Bertram, who kindly contributed the following article, was the first speaker to address the ENHG in 1976 when he gave a talk on dugongs. He made his journey to Abu Dhabi on that occasion by car. The following year, while flying over the same route on the way to the Far East, he fulfilled a promise that he made the previous year by writing the following note on pearling for the Bulletin.)

The Persian Gulf in the past vied with the waters of Ceylon (and I use these two old world names) in the production of the great majority of the pearls fished each year and of the shells taken for inlay work. Pearls are produced by several species of marine oysters. They lay down the pearly nacreous material over chance intrusions such as tiny sand grains or other extraneous material. Year by year, once the process has started, further uniform material is deposited until the pearl is produced.

The pearl oysters live on the bottom in warm seas, especially the relatively shallow pearling banks, which are areas of the bottom which can be reached by naked divers, at depths, roughly speaking, of less than 100 feet. Pearling was a cruelly hard means of livelihood and the physical damage to the divers was considerable, but so were the hard-won rewards. The pearling season in both areas was a great annual event of which there are many descriptions in the literature.

Here I will deal only with pearls rather than the production of shell, the commercial demand for which has risen and fallen remarkably in the past century.

Sometime during the last century, ingenious Japanese operators began to inject small sand grains artificially into oysters, which then were returned to the sea and kept under observation, or "cultured". Some of the treated oysters then produced saleable pearls at far lower cost and effort than in the wild. The technology was rather slow to develop, however, and the resultant pearls were usually rather small, inferior, and, to the cognoscenti, visually distinguishable from the natural pearl. For many years the pearlers of the Gulf and Ceylon were little affected by competition.

In more recent years, in the 1920s and 1930s, the picture changed rapidly. The technology of pearl production advanced and virtually killed the traditional fisheries.

I will briefly describe the modern pearl production of Torres Strait and Cape York, at the northeast tip of Australia. My wife and I viewed the operation there in 1965, being shown round by a Director of a joint Australian-Japanese company.

The process and technique is in strange contrast with the past. The divers now practice a less dangerous trade from local schooners, collecting young oysters from the bottom with air-breathing apparatus, and are paid by the piece. Any oyster four inches across and over will do. The species of oyster which is used will grow to about nine inches across and is capable of producing the biggest pearls. The collected oysters are kept in tanks briefly and then transferred to wire baskets, rather like toast racks, that hang from floating rafts at the surface. There in serried ranks, and acres in extent, the oysters are lapped by the warm surface waters so rich in plankton. And there the many thousands of oysters grow each in their allotted slots watched year by year by careful technicians who grade them, clean them, x-ray them and finally harvest them a few years later.

But first each oyster must be seeded and forced open with a wooden wedge, so that the skilled operator can insert the necessary nucleus around which will form, in proportion of the oysters, a perfect pearl.

This is not the place to explain the anatomy of the oyster. Suffice to say that the "mantle" is that part of the oyster with a specialist tissue whose function is to lay down the nacreous pearly layer which lines the shell, and to keep doing this throughout the life of the oyster as it grows and thickens. The seed must therefore be implanted in the mantle tissue, and therein lies the skill of the operator. The actual "seeds" implanted are small spheres about 3mm in diameter ground from the carefully cleaned and purified shells of Mississippi River oysters. An odd choice, but this nucleus has so far proved most efficacious.

Once seeded, the oyster is allowed another year to grow in its basket. Then it is x-rayed. If a pearl is visible, the oyster is allowed another couple of years to feed and grow. If no pearl is visible, then the mollusk is forced open again and another kind of nucleus (sometimes several) is inserted, this time perhaps a mere hemisphere which is forced down between the mantle and shell, there to grow to form blister pearls, of small value but useful for decorative purposes in the Far East.

Thus are produced the modern pearls which in general surpass in size the traditional ones. The biggest pearls from the particular oyster species of Torres Straits can be grown in 14mm diameter. At the end of the season, I was shown two huge polyethylene bags full of these enormous pearls, 1.5cwts of them, an impressive sight, but still needing a special washing process before they show their full luster. While inspecting these bags of pearls, I asked how many pearls were produced in the culture areas of Japan knowing that these were smaller pearls from another oyster species growing to no more than 9mm in diameter. The answer was "41 tons." That is why the traditional pearling of the Gulf and Sri Lanka has now all but died out.

Readers may care to refer to the article on page 10 of Bulletin No. 2 (June 1977) which briefly describes the earlier economy of Abu Dhabi, the importance or pearling as a generator of cash, and the serious local effects of the collapse of pearling when cultured pearls came on to the market.