ISTR that round beads are used to form cultured pearls. How big are they in relation to the finished pearl? Is it a small nucleus with a large amount of nacre? Or is it a large nucleus with like a micron of nacre?
According to the article below, it’s a very thin layer on the surface of a bead that is implanted at almost the size of the desired product.
-the article contains this image (drawing) comparing cross-sections:
That looks pretty thin!
I guess it makes for a short culture time and a reliable supply of uniform product. I don’t think it was always done that way though - I believe earlier efforts at cultivating pearls may have merely used grains of grit as seeds.
I know that some cultured pearls are considered better than others (Mikimoto comes to mind.) Are they made the same way, or are they a higher percentage pearl than bead? In other words, what makes the better ones better?
That’s it. Mikimoto pearls are allowed to form for longer periods of time, then those with surface imperfections, off-round shapes, poor color, etc. are weeded out to leave only the finest ones to be sold under the brand name. They can have coats thicker than 0.7 millimeter.
Older South Sea pearls, grown in a different oyster, were allowed to develop their pearls slowly and can be found with nacre a millimeter thick. More recently, nuclei almost the size of the finished pearl are being used, with benefit for the pearl farmers’ wallets, but thin nacre layers leave the pearl at risk of wearing down or shattering easily.
Jewelers and pearl connoisseurs learn to pick out the better quality strands by the quality of their luster. Some cheap specimens clearly show the layers of pearl bead inside.
Just last week I saw a slide show of some of the “irritants” being injected into the mollusks. I definitely had the impression that they were smaller – perhaps half the size. However, I didn’t see the finished product, so…
For some reason, most of the materials used as “irritants” for cultured pearls come from the Tennessee River. They use them even in Japan.
The largest freshwater pearl farm in the US is about a hundred miles from Nashville. I want one!