Mikimoto first opened a pearl accessory store in Tokyo's Ginza district and exhibited his pearls at the World Exhibition in Paris in 1937, winning global fame.
The only difference between a Cultured Pearl and a Natural Pearl declared the experts, (to the delight of Mr Mikimoto) was the artificial "nucleus" at its heart, but otherwise there was no difference in the structure.
If the pearls are approximately 75 years old they could be either early cultured Mikimoto Pearls, simulants, or Natural pearls.
Like all valuable gemstones, natural or native pearls have simulants. The difference in the lightly rougher layers of cultured pearls and natural pearls can often be detected by rubbing them against the teeth. However a more reliable method is to inspect the drill holes.
Under microscope the typical edges of overlapping layers of nacre are absent from the imitation pearl. A needle inserted into an angle into the drill hole can be used to detect any soft wax filling of the rarer hollow-sphere variety.
X--ray is the most reliable method to test if a pearl is natural pearl or Cultured pearl.
