WAYS OF THE WILD.

Auckland Star, Volume LXVII, Issue 193, 15 August 1936, Page 1

WAYS OF THE WILD.

LOCAL PEARLS.

NO FORTUNES TO BE WON.

(By A. W. B. POWELL.)

I have frequently been asked if the finding of valuable pearls in Kew Zealand waters is a possibility. Unfortunately, there is little likelihood of anyone making a fortune from this source in our seas. Pearls do occur, and quite frequently too, in some shellfish, but they invariably lack the lustre and glow of their precious rivals from the tropics.

The reason why fine pearls do not occur in Ne"' Zealand is that none of our possible pearl-secreting shellfish have the required lustre in their shells; for, after all, a psarl is formed by a shellfish of the identical material with which its shell is lined, and if this material, termed nacre, is of inferior quality the associated pearls cannot fail to be likewise.

Pearls are formed through the endeavours of certain shellfish to seal up a source of irritation caused by the intrusion of some foreign material into their shells. A speck of grit, a fragment from the shell of tlie shellfish concerned, or even the presence of a living animal parasite within the shell, may serve as the nucleus to a pearl. The pearl grows in size as the shellfish from time to time covers the nucleus with layer upon layer of nacreous material. As the layers are applied evenly i truly spherical pearl is a rarity, for the nucleus must approach spherical form also, otherwise the resultant pearls are of irregular shape.

True pearls are loose in the folds of tl lantle of the animal; blister pearls are irregular pearly bodies adherent to the inside of the shell. Both blister pearls and true pearls are found in several different kinds of local shellfish.

Mussel's Black Pearls. Perhaps the most prolific local producer of pearl processes is the common mussel, but these pearls are most irregular, never with a lustre, and certainly of no value. Mostly the mussel has blister pearls and these are usually formed as the result of boring activity from the exterior of the shell by a tiny boring sponge, Clione, or else as the result of sand within the shell. The common spiny horse mussel, Atrina zelandica, is worthy of attention as a pearl producer, for it frequently has numbers of pearls in a mantle cavity of the animal. Usually these pearls are perfectly spherical in shape,-and dull to jet black; unfortunately, they are seldom of any •size. It is passible that a pearl from this species combining large size with colour and lustre may have a value; if so I have missed my chance of making a fortune, for some years ago I lost overboard from a local trawler just such a pearl. It fell from the folds of the animal as I was opening the shell.

Even the Auckland rock oyster is a pearl producer, but it is very rarely that one of good size, shape and colour is found. These pearls are usually white with a faint pearly sheen and tinged with dull purple. Very rarely a perfectly spherical oyster pearl completely tinged with purple may be found, and these definitely have a value.

At Whangaroa and in the Bay of Islands the golden oyster, Anomia Walteri, produces at times very attractive little pearls of a lovely golden hue, but here again lack of size and regular shape is detrimental to, them for commercial purposes.

The most attractive pearls from a New Zealand shellfish comes from the paua, Haliotis iris; iris meaning a rainbow, and this very aptly describes the brilliant little gems obtainable from this, one of our most handsome shellfish, well known as the shell with a row of holes along one side, that was used extensively by the Maoris for making inlaid eyes for their carvings and fishing spinners for catching the kahawai and kingfish. Some years ago I found three loose pearls and an attached or blisterpearl in one paua, from Muriwai. The blister pearl was caused by a small boring bivalve shellfish, Saxicava, which had attacked' the paua shell from the outside; it then became a race between the boring activity of the Saxicava and the ability of the paua to thicken this weakened spot in its sholl, by applying from the inside, layer upon layer of iridescent material.

At one time the fishing of paua shells for pearls was carried on commercially at the Chatham Islands, while at the present time, trinkets made from the shells are becoming increasingly popular.

In the Distant Past. Even the ordinary cockle has been known to produce pearls. In the Auckland Museum collection there is an excellent spherical white pearl almost Jin across, lying in a cavity near the outer edge of one of the valves of a. large cockle, found some years ago by Mrs. M. Mouat at Devonport. A pearl so near to the edge of a shell is very unusual, for a bivalve shellfish should have no difficulty in expelling any foreign substance from this region of its shell by the simple operation of opening and closing its shell quickly. Any grit is normally expelled by the outflow

of water as the valves of the shell are snapped together.

Although precious pearls are not obtainable from local rshellfisji at the present time, we have evidence that they occurred in New Zealand seas in the dis'tant past. _ . In 1922 Dr. ,T. Marwick, of the Geological Survey Department, Wellington, recorded the finding of two fossil pearls from the * mid-Tertiary at Hawke's Bay. It is almost certain that they were produced by a large extinct bivalve, Pedalion, distantly related to the modern true pearl oyster. One of these pearls, now in the Auckland Museum, is a perfect sphere of two millimetres in diameter, and was found in fossiliferous marine clays beneath the limestone at Petane. The other, five millimetres across, but of irregular shape, was from the bed of Okauawa Creek, Hawke's Bay. The age of these fossil pearls is estimated at about 3,000,000 years.

No account of - pearls would be complete without reference to that famous Japanese, Dr. Kokichi Mikimoto, whose research and industry has made possible artificial pearl culture. Having in mind the early Chinese art of inserting metal images and other small objects ivifchm the shells of river mussels, ancl ir.diicuiS' the animal to cover these objects "i, layers of pearly material, I>r- o m „ r ; n e established a pearl treated by pearl oysters are similarly t f the insertion of a s]^ ant j e of the material within eedg to encase, animal, which theni p with layers of this source °f irrita th , m JS pro(formed Sat ntally.