Understanding Grading for Faceted Gemstones at Rio Grande

In this article, learn why some gemstones are graded and how Rio Grande grades our stones.

Last edited: 7/15/2019
Oval-cut emeralds arranged from AAA-Grade to C-Grade

Why are some gemstones graded? What’s the difference between a AAA-grade sapphire and a AA-grade sapphire? Or between a AAA-grade faceted amethyst and a AAA-grade amethyst cabochon? In gemology, there is no standard for grading gemstones and that makes it confusing for anyone without extensive gemology knowledge.

At Rio Grande, we grade our gemstones to ensure repeatable standards, so you can rely on the quality of the stone when you order from us. There are three factors taken into consideration when grading gemstones: color, clarity and cutting quality/precision.

Each gemstone material has its own unique set of characteristics. For example, some gem materials, like topaz, are prized for clarity, while others, such as emerald, are prized for their color and nearly always have inclusions. Because of this, the standard for each grade depends on the type of gemstone: AAA-grade sapphires will not have the same clarity as AAA-grade emeralds. The guide below shows, at a high level, how Rio Grande approaches gem grading.

AAA-Grade Amethyst
Excellent quality. These gemstones display a superior clarity, color (or lack of color), and cutting precision; they are the best gemstones Rio Grande offers.
AA-Grade Amethyst
Very good quality. These gemstones display exceptional clarity, color (or lack of color), and cutting precision.
A-Grade Amethyst
Good quality. These gemstones display desirable clarity, color (or lack of color), and cutting precision.
B-Grade Amethyst
Commercial quality. These gemstones display less desirable color and clarity attributes. Cutting may have minor defects.
C-Grade Amethyst
C-Grade (or below)
These gemstones typically have noticeable defects. They display poor color and clarity attributes. Cutting may exhibit moderate flaws. Rio Grande does not generally offer gemstones of this grade.

Before any cutting happens, gemstone rough is analyzed and sorted. The highest-quality rough is cut into faceted gemstones. The next-best rough gemstone material is cut into cabochons. Gemstone beads are made from the third level of rough. The remaining rough gemstone material is used to produce abrasives and for other commercial uses. Because this sorting takes place before cutting, a AAA-grade bead will never have the same quality as a AAA-grade faceted gemstone of the same stone material.

Have questions or need help sourcing the perfect faceted gemstones for your jewelry design? Contact the Rio Grande Gem Source, our graduate gemologists, Chris Hoffman and Shannon Demoulin, are always happy to help.

Gemstone Grades At-a-Glance

Aquamarine grades AAA through B

Aquamarine, grades AAA through B

Emerald grades AAA through C

Emerald, grades AAA through C

Ruby grades AAA through C

Ruby, grades AAA through C

Sapphire grades AAA through C

Sapphire, grades AAA through C