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HARVESTING OF POLYNESIAN BLACK PEARLS

HARVESTING OF POLYNESIAN BLACK PEARLS

If, at two years, all of the indications are good, the oysters are harvested. A number of farms now have two or more harvests a year. At this time, the oysters are brought to the installation or laboratory Where the initial insertion took place and are opened by a technician who then examines the
interior.

If the operation is successful and a pearl is found, it is removed carefully. The harvested pearls are washed, dried, and lightly polished by rubbing in salt in preparation for sorting and grading. On a few of the farms, the oyster may be reoperated on after a period of rest (V Dockendorf, pers. comm., 1989). On average, 55% of the oysters will accept the operation the first time. A return of 30% commercially acceptable pearls is considered a very good harvest (C. Rosenthal, pers. comm., 1989).

If the oyster has rejected the bead nucleus, the technician will check to see if a “keshi” (mantle tissue-nucleated pearl) has been created from the piece of mantle tissue that was inserted. In any case, if the mollusk that rejected the bead is deemed healthy, another implant may be attempted.

Again, some farms will elect to make mabes at this stage rather than risk a second implant because of the high mortality rate for mollusks after the second insertion.

GRADING

Five factors are commonly used by the trade to grade Polynesian black pearls: color, luster, shape, size, and surface features. Color and Orient. In the context of black pearls, one of the most important factors, “color,” consists of two components: body color (the basic color presented by the pearl) and overtone (the hues seen superimposed on top of the body color). Body color can be subdivided into six groups: silver, silver blue, gold, brown-black, green-black, and black (figure 13).

Overtone is typically a mixture of colors that is best observed as the pearl is rotated. Created by light passing through the layers of pink, lavender, blue, “peacoclz” blue, gold, green, or a reddish purple called aubergine (after the French word for eggplant). The color most characteristic of fine Polynesian black pearls is a greenish blaclz (also referred to as “peacoclz”) that sometimes has an aubergine overtone. Because other South Sea pearl-bearing oysters may also produce silver, silver-blue, and golden pearls, these latter colors are more plentiful in the market and therefore may command a lower price than the various combinations of black-colored pearls.

Also caused by the passage of white light through the many layers of nacre is the rainbow like play of color that seems to hover about the surface of some pearls. Called orient, it is not always prominent in blaclz pearls, although it is readily visible in the finer grades. Luster. Luster is the quality of light reflections from the surface of the pearl. As taught in the current CIA pearl course, luster is considered high when reflections are bright and sharp, and low when tKe9 are weak and fuzzy. In blaclz pearls, much of the light is reflected from the surface, thus producing excellent luster in most. In the trade, this brilliance is called eclat, from the French word for shiny.

Shape. Shape can be divided into three main categories: round or spherical, symmetrical, and baroque. The most highly prized is the perfectly round pearl that will roll in every direction when placed on a flat surface (Lintilhac, p. 70). Symmetrical pearls are pear-, egg-, or button-shaped; some are evenly elongated. The baroque-pearl category
contains all the irregular shapes and is the most interesting to many pearl enthusiasts.

Currently, there is an abundance of baroque pearls from the South Seas (see figure 14). American pearl grower John Latendresse feels that the disproportionate number of baroques is due to the poor quality of bead that has been supplied to the Polynesian pearl farmers. His examination of black-pearl nuclei reveals that many are infested with parasites whose presence alters to bits of organic material on the surface of the beads (figure 15), referred to in the trade as wax. “Nacre won’t adhere to the nucleus in places where there is wax,” Latendresse explains. ‘As a result, you get baroque pearls” (Federman, 1985). The desire for improved quality and a steady supply has led black-pearl producers to find beads outside the traditional sources of supply in Japan (C. Rosenthal, pers. comm., 1989).

Size. Size is the most readily determined feature of a pearl. Pearl sieves, much like diamond sieves, with holes ranging from 9 mm to 13 mm, are used initially to separate pearls into batches. Polynesian black cultured pearls generally average between 9 mm and 12 mm. Since the diameter of the typical Surface. As is the case with all pearls, surface imperfections such as pits, bumps, ridges, cracks, and spots lower the grade on a Polynesian blaclz pearl. Rings, actually parallel furrows that encircle the pearl, represent an unusual though often attractive surface feature (figure 17). Most rings, according to Latendresse (pers. comm., 1989), result from the pearl being nucleated near the hinge of the two shells. In a cultured blaclz pearl, a line on the surface of the nucleus bead may produce rings (again, see figure 15).

Pearl Grading System. Systems used in the trade to grade blaclz pearls typically consist of a series of letters that indicate shape and surface features. Lintilhac (1987) describes one such system:

S = Shape
R = Round
D = Drop or pear
Brq = Baroque
But = Button
Circ = Circled (Ringed)
Surface and Luster (figure 18)
A = Pearls with a flawless skin and high brilliance with one pit or pinprick
B = Pearls that are less brilliant and have two or three surface blemishes
C = Pearls that are somewhat dull or have four or more surface blemishes
D = Pearls that are definitely dull or marred by deeper flaws A similar system used by Assael International is outlined by Federman (1987).

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