One of the most important quality elements of cultured pearls is the thickness of nacreous layer so-called “nacre thickness value”.

In 2022, we suggested “nacre volume ratio” based on the measurement results of 1500 loose pearls for a new evaluation index of “nacre thickness” of nucleated cultured pearls.

In this paper, we examine the evaluation of “nacre thickness” by measuring the Akoya peal necklaces around 6-9mm in diameter, which are the most commonly distributed as pearl products on the market.