Cultured Pearl Terminology

There are many interpretations on cultured pearl (s) terminology in the industry.

(via Gems & Gemology) According to H A Hanni, a leading expert in gemology, all cultured pearls are tissue nucleated.

The terms bead nucleated and tissue nucleated are often used. The combination of these two terms creates the idea that a cultured pearl is nucleated with either a bead or a piece of mantle tissue, and the term nucleation suggests that there is something in the center of the cultured pearl, either a bead or tissue graft. However, the former does not lead to a cultured pearl if no tissue is added.

And, since all cultured pearls start with a piece of mantle tissue, this expression does not adequately differentiate between the two types. It is thus confusing and of no use. Further, the term tissue nucleated causes people to think that the grafted tissue is in the cultured pearl. However, research has indicated that tissue cells from the transplant become part of the pearl sac and do not remain as a residue in the center of the pearl. They do not form a nucleus. The X-ray visible dark structure in the center of these cultured pearls is often a void and preliminary precipitation from the growing surface of what will become the pearl sac. The transplanted mantle-tissue cells that produce the nacre grow into a pearl sac by multiple cell division, making a small pocket. This pocket produces an initial crust of a CaCO3 on its inner surface, but this crust does not completely fill the space, leading to the cavity in the center of a beadless cultured pearl.

H A Hanni proposed the following suggestions to CIBJO commission:
- Omission of the terms nucleus, nucleation, bead nucleated, tissue nucleated.
- Use of the term grafting for the introduction of mantle-tissue cells (with or without a bead).
- Use of the term beading for the introduction of a material that gives the shape to the pearl sac (to grow or already present), regardless of the shape of that bead.
- Use of the terms beaded-cultured pearl and non-beaded (beadless) cultured pearl for the resulting products.

CIBJO have included the above proposals for their Pearl Book.