The six criteria of quality pearls
The diameter or size.
The larger the diameter of a pearl is, the more it is rare.
The diameter is expressed in millimeters. Until about 1940, the volume or mass
of the pearls is expressed by weight, or grain or carats. The unit of rank, which
is a quarter carat, has fallen into disuse, a pearl of twenty grains equals
five carats equal one gram. The carat is often used for beads current size. It
is convenient to specify the weight in the exceptional expertise of pearls. The
diameter of cultured pearls from Japan
and China,
and pearls is usually between 2 and 9.5 mm. The South Sea
pearls are usually 9 to 14 mm. It happens that some pearls are between 16 and
18 mm
The form.
Over the shape of the pearl is perfect, it is rarer.
Following descending order, the pearls of the most popular are: round, pear,
oval buttons, semi-baroque and baroque.
The color.
It should be as uniform and honest as possible, both in
white, creams, grays as blacks, it is almost always a second tone at the bottom
of spot color: pink, cream, green, blue, yellow. The colors are the most
popular white-pink or pink-silver. Then came white, cream, pink, cream, white,
green and gold. With regard to black pearls, the colors green, blue or aborigine
is in high demand.
The luster and orient (the brightness of the pearl).
The luster of the pearl is its ability to reflect more or
less light. It can be very bright to dull glossy and matte or vice versa. It is
due to the combination of two phenomena:
Gloss surface: the light reflection on the surface of the
pearl. It is normal and natural it is carried out with sea salt, fine bamboo
chips or nuts, it is fraudulent if it is artificially replaced by abrasive
chemicals that give a surface gloss ephemeral. In addition, some unscrupulous
producers coat with a thick coating the nucleus to be implanted in I'huitre
pearl. This will increase artificially the brightness of the pearl.
The deep luster, it is due to the decomposition of light
through layers pearl. More layers are thin and numerous, the better the
reflection of light that will enhance the luster surface.
The east.
The East is a reflection that has a iridescent pearl is also
the degree of brightness that comes from the pearl ("water of
pearl"). It follows from the decomposition and the refraction of light
through crystals of aragonite. More layers are thin pearl and many more will be
the pearl of the Orient. The East is a sense of depth due to the thickness of
the nacre. In the case of black pearls or very dark gray, the orientation
effect is almost completely canceled, because there is absorption of light by
the color of the pearl. Only the surface sheen is evident. The water
temperature also plays an important role in the brilliance of the pearls. The
warm waters are often relatively dull pearls because the pearl secreted layers
are thick. Conversely, cold water (Japan) provides the most brilliant
Pearls.
The purity, cleanliness and surface finish.
The purity of the pearl is defined in number or absence of
default. That is to say, growths, small depressions called pits, colored spots,
two-tone areas of surface scratches, streaks of shadow. By convention, the
presence of a single shot is not taken into account anyway because it will
break in half to mount the pearl in the ring or piercing to include it in a
necklace. The drilling will be precisely at the site of the bite unique.
The thickness of the pearl.
According to the Pearl Science Laboratory of Japan, good
quality pearls have a nacre thickness of 0.4 to 0.6 mm. and, exceptionally, to
0.8 mm. It is mandatory two winter seasons for this thickness, a continuous
immersion of 19 months. Pearls of ordinary quality, so-called inferior, less
than 0.3 mm. thick and are the results of 6 to 8 months of immersion, or a
season. The beads of 0.2 mm. thickness of nacre are the result of plus or minus
3 to 6 months of immersion. This quality is totally unacceptable and to the
small thickness of nacre, the nucleus is visible through the shell to the naked
eye
