Pearls are cultured everyday. It is a very organic process which can be difficult to control and yet certain aspects can be manipulated. For example, pearl color. Some pearl colors are considered more desirable than others so how do you get that cultured pearl color?
This was such a fascinating concept which was of great interest to me when I traveled to a cultured pearl farm in the Philippines, one which prefers to produced Golden South Sea Pearls. You see, South Sea oysters come in two types, a Gold Lipped Oyster which is essentially a shell with a gold ring around the edge or a Silver Lipped Oyster which has a shell with a silver ring around the edge. If pearl production was left up to nature, the Silver Lipped Oyster would produce a majority of silvery white pearls and the Gold Lipped Oyster would produce a majority of golden yellow pearls. But by the nature of cultured pearls, humans get to intervene on this cultured pearl color.
The thin layer of tissue that lines the inner shell of an oyster is the mantle. The mantle hold the epithelial cells which secrete calcium carbonate and conchiolin, the two ingredients responsible for creating a shell and a pearl. Calcium carbonate is the material and conchiolin is the glue that holds it together. And this shell that this tissue secretes? Well, it is the same color as the pearls that the oyster will produce.
When a saltwater pearl is cultured, a bead and a piece of tissue is inserted in the oyster. That tissue is from the mantle tissue of a donor oyster and it holds the epithelial cells which will secrete the calcium carbonate and conchiolin and form the pearl.
So, if you want golden South Sea pearls, you want your donor to be a gold lipped oyster that has the cells to secrete a gold colored pearl. Even if you place that bit of tissue in a silver lipped oyster, the odds are in your favor that the pearl will be a golden yellow color. And that is how you can naturally manipulate cultured pearl color.