| The thickness of
the pearl's nacre and its quality is what gives the pearl its unique
beauty. The thicker the nacre and the better the nacre quality, the
more lustrous, iridescent, and exquisite the pearl. Nacre thickness
determines the pearl's longevity: the thicker the nacre, the longer
the life of the pearl.
Pearl producing oysters in the warmer waters of Tahiti, the Cook
Islands and Australia produce nacre much faster than Japanese or
Chinese; some experts estimate production to be fifteen to twenty
times faster. This means that even if the pearl is left in the oyster
for the same amount of time as Japanese pearls - and black pearls
usually have a longer cultivation period - the nacre would be much
thicker.
Nacre thickness of high quality Tahitian South Seas cultured pearls
is thicker than other saltwater varieties, and the finest may be
40 to 50 percent nacre. In Tahitian black pearls a nacre thickness
of less than 0.8mm is considered a reject and is not able to be
sold locally or for export. In comparison, a nacre thickness of
at least 0.5 mm is considered Very Thick in the grading of Japanese
pearls. Japanese or Chinese saltwater cultured pearls average about
10 to 15 percent nacre of the total pearl diameter, and rarely exceed
30 percent. Nacre thickness of high quality South Sea Cultured Pearls
is thicker than other saltwater varieties, and the finest may be
40 to 50 percent nacre.
|
Ratio nacre to bead
2:5
|
Ratio nacre to bead
1.6
|
Ratio nacre to bead
0.7:6.3
|
|
Ratio nacre to total pearl
40% 2:7
|
Ratio nacre to total pearl
14% 1:7
|
Ratio nacre to total pearl
10% 0.7:7
|
As of July 2002, the new minimum standard for Tahitian black pearl
nacre thickness was changed from 0.6mm to 0.8mm. Quality rather
than quantity is focus of today's black pearl producers.
|
