Japan Gem Research Laboratory

Our diamond grading is typically based on the 4C criteria, which are:

Carat: This measures the weight of the diamond. 1 carat equals 200 milligrams, and it's divided into 100 points. Larger diamonds are often rarer and more valuable.

​

Color: This describes the diamond's color purity. The color grades from the Gemological Institute of America (GIA) range from D (colorless) to Z (noticeable color).

​

Clarity: This describes the level of flaws, both internal and surface, within the diamond. Clarity grades range from internally flawless (IF) to imperfect (I3).

​

Cut: This describes the quality of the diamond's cut, including its reflection and refraction of light. Cut is graded as ideal, excellent, very good, good, fair, and poor.