There are a great number of pearls whose colour has a yellowish tinge. This alone is a mark of inferior quality.
It
is very probable that pearls possessing this yellowish shade exist
normally in the shell. Taver-nier, however, thinks that all pearls are
white, and that the yellow tint is induced by putrefied products,
resulting from the treatment of the shells in their places of
production; the pearl-shells being left in the open air that they may
open of themselves after the death of the animal. The work is thus
accomplished without any expense, and without risk of breaking the
pearls, an accident that occurs very frequently if the shells are
opened artificially. In support of his theory Tavernier states a fact,
which, if established, would be conclusive; which is, that yellow
pearls are never found in shells that have preserved their water.
The
shells in which pearls are found belong to several families of the
large class of mollusca; but the most important of all is the—
Avicula margaritifera, Bruguiere; Pentadina margaritifera, Lamarck.
This species not only produces the pearl, but furnishes to commerce
vast quantities of mother-of-pearl of the kind most valued.
There is a prevailing idea that mother-of-pearl and the pearl are of the same nature; and, in con-
