Though the luster of pearl is very beautiful, it cannot endure the test of long time. Generally speaking, after several decades the pearl will become the common yellow and loose the beautiful pearl luster at the same time.
Why does the pearl jewelry become yellow after wearing for a long time? It is mainly because of the unstable physical property of the aragonite mineral composed of the pearl. After a certain time, it will be the common calcite. Though the chemical elements between aragonite and calcite are the same, their crystallization form and luster have much difference.
After the pearls become yellow, there is still recovery method, and that is soaking them into the dilute hydrochloric acid. It can dissolve the shell which has become yellow and make the pearl reappear clear, bright, shiny and charming luster. If the color has becomes too badly, it will be unrecoverable.