The shape of the pearl is decided by the nacre formed with the secreted pearl quality.
It is evaluated as few, and as high than "[Shin;en]" it that the pearl quality is evenly secreted.

It is an evaluation of the following shape in the [akoya] pearl.

"Round" ･･･ [Shinkyuu] or near it spheroidal pearl. There is pearl
"Baroque. " ･･･ ruggedness that shape changes for the worse a little located from one
"[Semiraundo]. " ･･･ Maru evaluated highest in the quality element of shape to the middle of one
"Semi-baroque. " ･･･ [shin;en] and baroque that is the oval a little, and the one that shape has been distorted.

The thickness of nacre relates to the color and luster with durability and a good depth, and in the quality element, is the most important.
Moreover, the quality of the color, Terri, durability, and elasticity changes depending on nacre's quality, too.
The grade rises in the one that rolling is thick in high quality nacre.

It greatly influences the grade of the pearl by the number, the kind, the size, and the location, etc.

Small [kizu]	Middle [kizu]	large [kizu]	processing [kizu]

The grade lowers Sharp [namo] very brightly, and the reflection diffuses weakly high, and oppositely and the grade lowers to the slow one lowering of the quality of light to which the pearl reflects of a good reflection of light.

The color of the pearl is very complex.
There are implications with rolling and Terri, and are three elements that decide the color of the pearl especially greatly.

First, it acts and Terri of light. (How much is the crystal of "Aragonite" with which nacre is formed uniformly piled?)
Secondarily, the coloring matter. (material "Conchiolin" that composes pearl)
Thirdly, the organism. (Become a blue color with the organism etc. that the shellfish generates. )