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Although pearls are not cut or polished like all precious stones, they are often bleached before being marketed. Round pearls are also drilled, but otherwise they receive no assistance from the hands of man. The drilling is usually carried out before the pearls are offered to the Western markets, for drilling requires time and patience, both of which seem to be more plentiful in the East than in the West. The methods used are somewhat antiquated, but they are effective. The best possible results must be obtained; the holes must be clean, straight, and very small, otherwise the pearls will hang badly when threaded, and their value will also be reduced. The craft of drilling has been handed down through generations, and Europeans have nothing to learn from the native craftsmen, judging by results.

But, apart from market fluctuations, small defects in pearls make such a vast difference to their value that only a pearl expert is able to give a reliable opinion. A single pearl may be valued at $28,000 (£10,000) while a necklace composed of very small pearls, known as seed pearls, may be bought for $8.40 (£3). The unit of weight universally in use is the pearl grain, and later we shall explain the peculiar method of calculating values on the "base" system. Low quality and small seed pearls are, how­ever, bought and sold by weight, the Troy ounce being generally used. Other units of weight have been used in the past since the pearl oyster really thrives only in the warmer seas and oceans. The Persians, according to Athenaeus, sold pearls by their weight in gold, but modern methods are more exact and less costly.

The origin of pearls was a subject of much speculation by many early writers. The belief that they were formed by drops of rain falling into certain shells and afterwards hardened by a secretion of the oyster was quite common. The real composition of a pearl and the method of its natural formation are, in fact, something which only comparatively recent scientific research has revealed to us. We now know that this beautiful gem is the product of "a mollusc, a shell fish, and although of organic origin, it is com­posed principally of mineral matter. For this reason, it cannot be strictly regarded as a gem stone, although it must be recognized as a precious gem.

All bivalves, that is, those shell fish which possess two half shells, are capable of producing pearls, but as so few pearls are actually found, it is necessary to say something about the animal which first builds the shell and later, under certain favorable con­ditions, also produces the pearl.

It is impossible to assess the relative beauty, rarity, and value of the different precious stones, but a perfect pearl of some size (about ten grains and over) is certainly one of the rarest of gems. This is despite the fact that it cannot be classified as a stone, since it is the product of a certain class of shell fish. A beautiful rosee iridescence, spherical shape, complete absence of surface blem¬ishes—these are the qualities that make for perfection, and this is what the connoisseur seeks yet seldom finds in pearls of appreciable size. Hence the value of this gem lies in its genuine rarity of perfect specimens.

Some account of the mining for stones in Burma and Ceylon should be of interest since many of the methods used are charac­teristic of native gemming. These methods are very different from those employed in the huge industry of diamond mining in South Africa. In Burma, mining by modern methods and on a large scale has been tried with varying success, but in Ceylon, only the individual digger, or a small party, works the gem gravels with simple tools to discover the stones. In Burma, various methods of mining have been employed over a great number of years. The usual methods may be classed as the Twin (or Well), the Myaw, and the Loodwin.

In the first, a round pit is dug by means of simple tools, a hoe and an iron bar being generally used, and the loose earth to a depth of 20 to 100 feet is excavated. Hauling is done by means of a home made bamboo basket, which is suspended on the end of a length of bamboo, the length varying with the depth of the pit. A basket of stones on the other end acts as a counterweight. The surface earth generally consists of a hard clay, and this is removed until the gem bearing strata is reached. This "byon," as it is called, is examined closely, and then lateral tunnels are dug so that no gem bearing earth is missed. For holding up the sides of the trenches, timber and brushwood are used; if water is struck, a simple pump made from bamboos is used for bailing. During the rainy season, the workings become flooded and the pits have to be abandoned for hillside workings.