Because of differences in the way gems form and their varying chemical compositions and crystal structures, certain types of colored stones are inherently more included than others. For example, gems like aquamarine have a potential for better clarity than emeralds. This is why different gem varieties are assessed according to different clarity standards.
The GIA Colored Stone Grading System is designed to help you assign meaningful clarity grades to gemstones in the marketplace. GIA divides colored stones into three groups, based on their potential clarity:
- Type I stones are usually eye-clean, with no inclusions visible to the unaided eye. These include aquamarine; pink, green and yellow beryl; chrysoberyl (excluding cat’s eye); spodumene; green tourmaline; blue zircon; and tanzanite.
- Type II stones typically show some eye-visible inclusions that don’t detract from the stone’s overall beauty. These include andalusite, alexandrite, corundum (excluding stars), the transparent garnets, iolite, peridot, spinel, quartz, all colors of tourmaline except green and watermelon and zircon.
- Type III stones are almost always included. Because of the environment they grow in, they frequently contain abundant inclusions of other minerals. They’re often highly fractured, and harsh mining and processing techniques might create more fractures or make existing fractures larger. Type III stones include emeralds, red beryl, and watermelon tourmaline.
Photo: Joel Beeson/Robert Weldon/Tino Hammid Courtesy: GIA.
Resource: Amanda. #eClarity