Colour, Lustre, and Value

The lustre of pearls is nacreous, which means resembling mother-of-pearl, a lustre due to the minute undulations of the edges of alternate layers of carbonate of lime and membrane. The lustre of some pearls exists only on the surface; the outer surface of others may be dull and the inner lustrous. The specific gravity of the pearl is 2.5 to 2.7; hardness, 2.5 to 3.5. The shape varies and the range of size and weight is great. The smallest pearl in commerce is less than the head of a pin; the largest pearl known is in the Beresford Hope collection in the Museum at South Kensington, London. Its length is two inches and circumference four and a half inches. It weighs three ounces (1818 grains).

Although the whiteness of the pearl is constantly used for comparison, pearls range in colour from an opaque white through pink, yellow, salmon, fawn, purple, red, green, brown, blue, black, and in fact every colour and several shades of each; some pearls are also iridescent. The colour and lustre are generally that of the interior shell surface against which the pearl was formed.

The beauty and value of the pearl, in brief, depend upon colour, texture, or "skin" transparency or "water," lustre, and form; pearls most desired are round or pear-shaped, without blemish, and having the highest degree of lustre. The queen of existing pearls is La Pellegrina now in the Museum of Zosima, Moscow, Russia. La Pellegrina is perfectly round and of an unrivalled lustre. It weighs 112 grains.

While individual pearls or strands of them may be worth a prince's ransom, their beauty and value are not immutable; pearls may deteriorate with age or be sullied by the action of gases, vapours, or acids, and the known methods for their restoration to their original appearance and value are not always successful. Fine pearls should be carefully wiped with a clean soft cloth after they have been worn or exposed, and kept wrapped in a similar fabric in a tightly closed casket.

Pearls are found in nearly all bivalves with nacreous shells, but the principal supply is derived from a comparatively few families, led by the aviculidae, Unionidae, and Mytillidae. The first group includes the pearl oyster of the Indian and Pacific oceans, from which has come the bulk of the world's pearls; the second includes the unio, or fresh-water mussel of North America; and the third is a family of conchiferous molluscs, mostly marine, the typical gems being Mytilius edulis, or true mussel, which has a wedge-shaped cell and moors itself to piles and stones by a strong coarse byssus of flaxy or silky-looking fibres. The distribution of these molluscs is world-wide.

"In all ages, pearls have been the social insignia of rank among the highly civilised," writes W. R. Cattelle in his standard book The Pearl. First lavishly used by the princes of the East for the adornment of their royal persons, as the course of empire trended westward the pearl followed the flag of the conquerors, and thus, in time, as Rome's power and affluence grew into world-control, her treasure of pearls grew to vast proportions and became identified with the social eminence and arrogance of the Caesars and patrician Rome. To-day the market for the best in pearls of recent finding, as for all new products of precious stones, or for famous jewels, whose owners' changing fortunes bring them to the parting, is within the new regime of Croesus represented by the multi-millionaires of the United States. The world's best buyers of jewels are not always as willing to have their princely expenditures known as is generally believed, and the names of some of America's heaviest purchasers of gems have not been revealed by the dealers. It is authoritatively stated that the finest single strand of large pearls in existence was recently acquired by a Western millionaire of the United States. The strand is composed of thirty-seven pearls ranging from eighteen to fifty-two and three-quarter grains each, the latter being the largest central pearl. The pearls combined weigh 979 3/4 grains, and the strand is said to have cost its possessor $400,000.