Sweet-Water Pearls.—Pearls from fresh-water.
True-Pearls.—Pearls formed of nacre as distinguished from similar formations which are not nacreous.
Twinned-Pearls.—Pearls enveloped together in one or more layers of nacre.
White-Shell.—Pearl-oyster shells with nacre white to the edge.
Yellow-Shell.—Pearl-oyster shells with yellowish nacre.
GENERAL CHARACTERISTICS OF PEARLS AND SHELLS FROM THE VARIOUS FISHERIES
Arabian Sea.—Pearls have fine orient, but the color inclines to yellow.
Shells are larger than those of Ceylon but of little value for mother-of-pearl: iridescent, black-edge m. of p.; known as Lingahs.