There are three
basic ways to manufacture paste (paste, imitation, man-made, etc.)
pearls today in China, Japan and other parts of the world:
1) Using a plastic bead centre formed by injection moulding.
2) Using a white glass bead centre.
3) Using a central bead made from shell.
The shell method is the most convincing in appearance and weight, and
is also the most expensive. The plastic bead method is the most
economical, and the glass bead technique falls in between having
become more economical in recent years due to manufacturing equipment