Hi Lisa, by rejected nuclei I mean the nuclei that the oyster either rejected completely or where a pearl didn't form properly. This can be either a nuclei that is spat out not long after grafting or a pearl that is badly formed, calcified or heavily crusted or badly deformed. With larger sizes we'll try to cut them back to nuclei for re-use although smaller sizes are not worth working as replacements are far cheaper. These rejected or 'reject' pieces are usually found within the oyster as in Australia they typically do not use nucleus rejection nets, as some do in Tahiti.
When the nucleus is rejected, it can either be fully rejected from the shell and fall to the ocean floor (or collected in rejection nets) or it can be rejected from the 'pearl sac' yet remain within the oyster, or even remain in the pearl sac but not form properly.
The tear drops I have were inherited from a client who is now out of the business. We have never manufactured them but I believe they are shaped by hand - although not 100% certain.
Nuclei are generally cut from square or near square, formed into rough rounds and then final processing to get to a true round shape which is then polished. The drops would be specifically ground from pre-cut pieces to suit the end product/size required.
We have found some pretty interesting things when undertaking recycling, particularly various nuclei materials as well as shapes, etc.