Lesson 4: Gemology Cheat Sheets

Step 3: Practical Gemology

Lesson 26

Use these gemology cheat sheets to review color and clarity grading, as well as special information on diamonds and opals. You can also review basic gem identification testing procedures for the refractometer, polariscope, and specific gravity.

Each section contains links to International Gem Society (IGS) articles that discuss these topics in greater detail.

Evaluating Colored Gemstone Clarity

Clarity grading involves examining a gem’s transparency, inclusions, and blemishes.

The Gemological Institute of America (GIA) has devised a clarity grading system that, first, groups colored gemstones into three types:

GIA Clarity Types

Type I
Usually eye clean
Type II
Usually included
Type III
Almost always included
Chrysoberyl, yellow and green
Quartz, smoky
Spodumene, all
Tourmaline, green
Zircon, blue
Corundum, all
Garnet, all
Quartz, amethyst

Every Gemstone Is Unique - Here's How The Experts Evaluate Them

in this training-course, discover the tools, tests & valuation process used by expert gemologists for colored gemstones, opals & diamonds

Course: Hands-On Gemology: Gemstone Identification Grading & Testing
Purchase Course: $79.00
Skill Level: Intermediate - Advanced
Lessons: 60
Time: 480 min