Acceptable Finishing Techniques for Pearls
This woman is working on a pearl farm to open and clean oysters for their pearls.
The bowl of pearls at her feet will go through a washing and, most probably, a bleaching process with hydrogen peroxide to lighten and improve the uniformity of color in the pearls.
Maeshori is a form of new luster treatment that involves the heating and cooling of a pearl in order to cause its luster to be artificially enhanced. It is a Japanese word that literally mean before (mae) treatment (shori). Originally, maeshori involved dipping pearls in a solvent - mainly methyl alcohol to clean them and remove impurities so they could be bleached more efficiently.
This may be more than you wanted to know, but there are a lot of accepted treatments for pearls that enhance their beauty.