It is hard to get sufficient shell to afford enough beads in the larger sizes, with the result that these are expensive and some sizes not available. Also, mussel shell has a major disadvantage as a nucleus. It is a material that has directional properties. The shell layers are bound together by an organic matrix and the layers can part during bead manufacture and during drilling of the finished pearl. We have focused on natural dolomite as a stating point for our nucleus development.
Dolomite has major drilling deficiencies as a pearl nucleus.
The main one is that the material is too hard for easy drilling. Materials we have tried will drill slowly, but also cause rapid drill wear. This in turn can lead to rapid over heating of the nucleus and possible cracking of the structure. We are aware that some Korean and Japanese firms are offering dolomite to farmers as nuclei at discount prices to shell. We find this material very slow drilling giving rise to excessive drill wear.