In its purity, liquid beauty, and charm of romantic and poetical association the pearl--aristocrat of gems--leads even its peers of the highest rank, the diamond, emerald, ruby, and sapphire.

The sea-gem has throughout all recorded time formed the fitting necklace of feminine royalty and famous beauty; the state decorations of dusky Oriental potentates and their principal treasures have been pearls.

From the ocean's bed and the turgid streams of midland North America, from almost anywhere that is the habitat of the oyster or the humble mussel come these pale, lustrous treasures that may prove to be almost priceless.

The existence and recognition of the beauty of the pearl as a personal ornament and treasure is undoubtedly prehistoric on every continent.

The discoverers and conquistadores from old Spain found quantities of them in the western Indies, on the Spanish Main, in Florida, Mexico, and Peru; the mound-builders of North America possessed them; in the far East they were cherished centuries before the then Western world of Europe knew them; there is said to be a word meaning a pearl in a Chinese dictionary four thousand years old, and who knows how old is their presence in India.

Pearls were in the jewel caskets of Egypt's Ptolemies; and the first jewel mentioned in the most ancient decipherable and translatable writings extant is the pearl, and its identity is unquestioned, because the gem of the sea is solitary among jewels and is not to be confounded with the hard mineral gems which, even to-day, with all the advance in scientific knowledge, are constantly becoming mixed in the minds of men.

From written records the modern ken of pearls extends back about twenty-three hundred years, and we hear of them in the writings of Pliny, the indefatigable investigator and disseminator of what he believed to be facts about almost everything in nature, who four hundred years later gathered together the knowledge of his day about pearls and included it in his voluminous literary grist.

In the technical literature of the United States National Museum, the pearl is coldly and remorselessly comprehended under the generic term "carbonate of lime" along with the beautiful but less valued coral, which is also a product of the sea; and marble, which concerns architects and sculptors, more than gem fanciers; and calcite and aragonite, which are varieties of satin spar and far down in the gem stone scale of hardness.

It seems almost like desecration to reduce the lustrous pearl of peerless beauty and royal and romantic associations to the concrete mineralogical base of carbonate of lime; but thus are the insistent requirements of the mineralogists conserved.

Therefore, pearls are concretions of carbonate of lime found in the shells of certain species of molluscs. An irritation of the animal's mantle promotes an abnormal secretory process, the cause of the irritation being the introduction into the shell of some minute foreign substance, sometimes a grain of sand.

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.

Having considered the factors bearing on the value of pearls, we will next consider briefly their physical properties.

The specific gravity is less definite than with minerals and varies between 2.65 and 2.70. It may be even higher for pink pearls.

Physical Properties. In hardness pearls also vary, ranging between 3 1/2 and 4 on Mohs' scale.

They are thus very soft and easily worn or scratched by hard usage. A case showing the rather rapid wearing away of pearls recently came to the attention of the writer.

A pendant in the shape of a Latin cross had been made of round pearls which had been drilled and strung on two slender gold rods to form the cross. The pearls were free to rotate on the wires.

After a period of some twenty or more years of wear the pearls had all become distinctly cylindrical in shape, the rubbing against the garments over which the pendant had been worn having been sufficient to grind away the soft material to that extent.

The luster was still good, the pearls having virtually been "peeled" very slowly by abrasion.

Care of Pearls.

This example suggests the great care that should be taken by owners of fine pearls to prevent undue rubbing or wear of these valuable but not extremely durable gems.

They should be carefully wiped after being worn to remove dust and then put away in a tightly closed case.

Pearls should never be allowed to come in contact with any acid, not even weak acids like lemonade, or punch or vinegar, as, being largely calcium carbonate they are very easily acted upon by acids, and a mere touch with an acid might ruin the surface luster.

Being partly organic in nature, pearls are not everlasting, but must eventually decay, as is shown by the powdery condition of very old pearls that have been found with mummies or in ancient ruins.

The organic matter has yielded to bacterial attack and decayed, leaving only the powdery mineral matter behind.

As heat and moisture are the conditions most conducive to the growth of bacteria, and hence to decay, it would follow that fine pearls should be kept in a dry cool place when not in use.