Answer from Research department
Quality of the nuclei .(anglais) 0704
As French Polynesia Pearl culture office we are totally concerned by your problem. Actually, several cases of broken pearls after drilling have been reported to our administration. The problem is known and most of the time due to the use of unsuitable quality of nuclei, especially nuclei made with Giant clams shell from China.
These nuclei are harder than usual Mississippi mussel nuclei and when you drill the pearl it may cause some over heating that can lead to the pearl destruction.
The research department is actually developing with some experts an instrument to detect the origin of the nuclei (mussel, giant clam, Bironite…). These detectors will be used to stop giant clam nuclei importation to French Polynesia as wished by the Government.
giant clam as pearl nuclei
Although the post was nearly two years ago, I believe that pearls cracking at the processing of drilling still exist. It is possible that the cracking is caused by incorrect drill bit. However, if you are an experience driller, the chances of cracking should be well within a small percentage. Most likely, it has to do with the nuclei.
In fact, giant clams used as pearl nuclei will cause pearls to crack at a much greater chance than the traditional Mississippi shells. Giant clams grow at a faster rate, bigger size and thickness. Hence, one clam produce many difference sizes of nuclei, but at a lower density than Mississippi shells.
I am very concern with this problem because my company sells pearls and manufactures our own nuclei. We are well experienced in the area and we do not have this problem because our nuclei is strictly made out of Mississippi shell.
Although the pearls have good luster, color, quality and price, please be careful.
Cracking pearls and correction
I would like to correct myself from the previous post on this thread. I'm uncertain about the difference in density between the Mississippi shells and the giant clam shells. But I know from the industry that the giant clam shells are a lot cheaper than the Mississippi shells, and can produce bigger nuclei and larger amount of nuclei from one single clam than one single Mississippi shell.
Originally Posted by jwong
We hear from the industry that when you drill through pearls having giant clam shell as the nucleus, the pearls will crack. We have tested it out ourselves, and found that this is true. The pearl will crack from the inside, hence it will have no value.
Giant clams from the industry mainly come from China and Vietnam, and other South Sea area.
I'm uncertain of what the effects giant clam nuclei have on shells and pearl farms, all i know is it devalues any good pearl. This is well-known in the industry. However, some bad suppliers might mix the two different kinds of nuclei together to lower their cost without telling buyers.