What is a Non-Nacreous Pearl?

What is a Non-Nacreous Pearl? Quite a word, isn’t it? Non-Nacreous! Well, let’s take it back to the word nacre. Does that sound a little friendlier? Pronounced with a long “a,” nacre is mother of pearl. It is the building block for a pearl. Nacre is that beautiful, lustrous material in the inside of a …