Although an organic product, the pearl is always ranked amongst the
most precious of gems, and is distinguished by being the only gem that
does not require the lapidary’s touch to bring out its beauties.
Ancient writers have accounted for the origin of pearls by saying
that they were formed of angels’ tears, or drops of dew from heaven,
which, during the midsummer nights, fell into the gaping mouths of the
pearl-oysters.
According to modern scientific investigation, the formation of the
pearl does not seem to be the result of healthy natural causes, but
comes from the efforts of the oyster to rid itself of some foreign
substance, like a grain of sand, a bit of shell or vegetation, or some
unwelcome visitor in the shape of a small water insect.
When annoyed by an intruding substance, the oyster begins to deposit
its nacre, or mother-of-pearl, in regular concentric layers around
the intruder, these layers gradually increasing in circumference
and forming the pearl. Thus, like an onion, the pearl is merely a
succession of layers or skins, starting from a small core, or nucleus,
which is always present, though often only of microscopical size.
Pearls have sometimes been found where the outer layer, or skin, as it
is technically called, has been discolored or otherwise injured, and
when this top skin has been carefully removed the result was a somewhat
smaller but perfect pearl.
This, however, is a very delicate operation, and at the pearling
grounds is only resorted to by men of experience. The composition of
the pearl is carbonate of lime, with a small proportion of organic
matter, and the specific gravity 2.5 to 2.7.
The pearl is affected by acids, and is easily calcined on exposure to
heat.
In color, the pure white, slightly transparent, is the most highly
prized; while in India and China the bright yellow colors are sought
after.
Decided colors, however, such as black, pink, and golden-yellow bring a
high price, and, in fact, black pearls, if perfect in color and shape,
are at present more valuable than any other kind.
The beauty and value of a pearl depend on form, quality of texture or
skin, color, transparency or water, and lustre or orient.
In form, the perfectly round shape comes first in value, then a finely
formed drop or pear shape, and lastly the oval or egg shape.
Pearls that are flat on one side and rounded on the other are called
boutons or button pearls. These are frequently found attached to the
shell, and are cut out and the bottom part smoothed and polished.
It is easy, however, to detect this class of pearls by the lack of
pearly lustre on the side that was attached to the shell.
When a pearl is rough and odd-shaped it is called a baroque, and some
extremely fantastic shapes are found, especially in fresh-water oysters.
The texture or skin of a fine pearl should be perfectly smooth and free
from all spots, indentations, wrinkles, or scratches.
Pure white is the desirable color for a gem pearl, but many others that
are slightly tinted with blue, pink, or yellow will pass for gems if
they are otherwise perfect.
The transparency or “water” of a pearl, while not existing in fact,
is still one of the requisites of a fine pearl; there must be an
appearance of transparency, which adds to the beauty of the gem.
To describe the lustre or orient of the pearl, the author can
only use the term pearly, as there is no other substance that
approaches the brilliancy and color of a pearl, excepting, of course,
mother-of-pearl—the nacre in the pearl-oyster.
Without orient or lustre, the pearl of finest form and color has but
little value.
Lustre is to the pearl what brilliancy is to the diamond; when the
orient is absent there is no life, no beauty.
Pearls are principally supplied by two groups of pearl-oysters or
mussels: the marine or meleagrina margaritifera, a round-cornered
square shell with very thick sides, measuring six to eight inches in
length.
The color of this shell is mostly blackish-green, but it is also
sometimes yellowish; the edges of the inner part of the shell are
black, but the rest of the interior is the beautiful mother-of-pearl.
The oyster itself is small for the size of the shell.
This specimen is found on the coast of Ceylon, Persian Gulf, Japanese,
Mexican and California coasts, the western shores of South America,
Brazil, West Indian Islands, Panama, Sooloo Archipelago, and the
northeast and northwestern coast of Australia.
The fresh-water or unio margaritifera is an even, egg-shaped mussel
found in brooks, rivers, and lakes in temperate zones in nearly all
parts of the world.
Some fine river pearls have been found in the United States, but most
of the American pearls are of a button or elongated shape, or are
baroques or fancy-shaped.
In China many people engage in the business of making small pellets of
clay or metal images, which in the month of May are introduced into the
river mussels (mytilus cygneus).
The mussels are replanted, and in November they are taken up again.
Some of the oysters die, but most of them are found to have been
actively at work covering the little pellets or metal figures with
nacre, and while no strictly first-class pearls are formed in this way,
many curious little pearl figures or gods are made and sold to the
curious or devout.
Pink or conch pearls are found in the Gulf of California and coasts
of Mexico, Bahama Islands, West Indian Islands, and in some rivers in
South America.
They seldom occur in regular shapes, and although they are termed pink
pearls, they range in color from red to pale yellow, and are often
found of a china-white color.
The pink pearl displays a wavy appearance and a peculiar sheen,
something like watered silk. As the pink pearl is seldom found
perfectly round and of a good color, such a specimen is very valuable.