Well, look at Mikimoto website. Click on the "About Jewelry" tab. There is info on how they grade their pearls, info on the different types of pearls, and how to care for them. They have basic info, on the quality of pearls, stuff you probably already know, but maybe not. I love Mikimoto pearls, they are beautiful. I have been blessed, and have a pearl necklace from them. I cried when I got them. It has always been a dream of mine to have Mikimoto pearls.
Good luck in your research. By the way, there is a Mikimoto store in the Venetian hotel in Las Vegas. Lil' Lori