I have heard about freshwater pearls or cultivated pearls before but I have never heard of mikimoto pearl. Some people often misinterpret the word "Akoya" as having the same meaning as “Mikimoto” but the fact is that they are totally independent of each other.
Strictly speaking, Mikimoto pearls are those cultivated under a strict patented process in the bays of Ise, Honshu, Japan. They are farmed in a tiny island located off the Ise coast previously purchased by the Mikimoto family in the 1930`s and has since then become a part of the rich international legacy.
Mikimoto deploys a worldly recognized grading method independent of the GIA grading standards to evaluate pearl quality. The highest quality pearl receives AAA rating and also has a "mirror like" reflection when compared to lower grade pearl. Most purchasers are not jewelers or appraisers, therefore they are not aware of the exact grade of their Mikimoto pearl. As such, they depend on valuation certification for insurance purposes.
For buyers who are really interested in distinguishing true high grade mikimoto pearls from cheaper freshwater or akoya pearls, you could inspect the pearls under microscopic magnification. Authentic Mikimoto pearls have distinguished roadmap patterns that experienced pearl jewelers will be able to identify them. However, like most of us who are not experienced pearl jewelers, the quickest way to inspect a pearl is to look for very slight rose tint, pink or undertone, which will not be found in 95% of any other Akoya pearl. This is the most important tip for beginners or other first time buyers to watch out for.
Mikimoto Pearl Video