Keshis, how does this happen?

[CLICLASP]

Hello everyone,

This is not my first keshis that show a very curious partly coated nacre look,
See on picture, it looks like if only a thin shiny nacre layer had covered a kind a baroque keshi-shaped nucleus, and under the nacre, it is dull and chalky
or
.. do I need new spectacles

thanks for advising from the experts

 

[Pearlgully]

Is that a freshwater keshi or a south sea keshi?

Is it possible that pearl is a "fireball" (bead nucleated freshwater)?




Gail

 

[jshepherd]

You mention that it is "partly" coated with nacre, but that would not be the case. The pearl has some nacre issues, but appears to be all nacre.
I have seen these sorts of chalky areas and spots especially in baroque saltwater like akoya.
Because the color is light and not dark it is not conchioline. It would rather be calcite concretions or aragonite platelets laid in disarray.
If the pearl is freshwater I am curious about your distinction of keshi, as it does not look like a regenerated pearl. The discoloration could be due to changes in water chemical content during cultivation (such as the currently popular "rust-stain" pearls), or over processing afterwords. If freshwater pearls are heated beyond the maximum allowable time they will develop chalky spots (although they usually turn dark, not total white).