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been
used to produce artificial or cultured pearls. A small object is placed
inside the oyster and then it is returned to water. After a year or two
the oyster is withdrawn and the pearl removed. In Japan by a
particular process the oysters are caused to grow pearls of a spherical
shape, very much resembling natural pearls. In the natural pearls,
growth is concentric whereas in the artificial growth is seen to be
parallel and only concentric layers are seen on the outer surface.
Pearls are composed largely of aragonite
white, faint yellow, bluish and even red, green and black. Translucent to opaque. Lustre: Pearly also iridescent.
The
best pearls have a spherical form, lustrous and iridescent, free from
blemishes and somewhat transparent. White ones are priced most. Pearls
of irregular shape are known as 'Baroque'. Flat pearls are known as
button pearls. Due to softness, it is easily scratched. The lustre is
affected by heat, acids or foetid gases. Age also causes deterioration,
and the lustre once lost cannot be restored.
Pearl
fisheries are operated along the Indian coasts, near Mannar between
India and Ceylon, the Persian Gulf, the Red Sea, Japan, Antarctic,
etc., also in rivers in Europe, America, China and Japan; so that there
are marine and fresh-water fisheries of oysters.
Boring and polishing. These
have to be done very carefully and done by the help of pearl dust.
After wearing on the body they are liable to lose lustre. They have to
be wiped by clean linen or silk and kept covered in a closed box.
Imitation
pearls consist of hollow spheres of thin glass coated with a
preparation from fish scales and filled with white wax. A translucent
white glass with a pearly lustre may also be used to imitate the gem.
Price of pearls.—Price
depends on their form, texture, transparency and lustre. Spherical
pearls fetch the highest price and those with fancy colours sell at any
price. Large
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