How to Grade Set Gemstones
Step 4: Gem Grading Lesson 4 Back to syllabus Few gemologists deal strictly with loose stones. Occasionally, most may have to grade set gemstones.…
Clarity Grading for Colored Gemstones
Don’t underestimate the importance of clarity, one of the Four Cs of gemstone grading. For faceted gems, basic clarity grading involves…
Advice for Determining Gemstone Value
Step 4: Gem Grading Lesson 9 Back to syllabus Many new gemologists buy low-quality gems believing they’ve found a real bargain. However,…
Destructive Gemstone Tests: Hot Point Testing
Hot point testing can determine if some gem materials are plastic imitations. It can also reveal if a stone is treated with wax or plastic. By Donald…
The Art and Science of Identifying Gemstones
Trigon inclusions are part of a natural, uncut diamond’s original crystal structure. These were photographed on the surface of a rough…
How to Test for Diffusion Treated Gems
Step 3: Practical Gemology Lesson 16 Back to syllabus Since diffusion treated gems are so common, gemologists must learn how to identify these…
Gemstone Magnetism: The Forgotten Property
Although gemstone magnetism isn’t a commonly tested gemstone property, it may be useful for making quick separations outside the lab. By Richard…
Gemstone Physical Properties
Step 2: Advanced Gemology Lesson 2 Back to syllabus The optical properties of gems attract our eyes and can give a cut stone a unique character. However,…
Gemstone Color Change Phenomena
People frequently ask me to explain how gemstone color change works. Some stones can change color under different types of light sources. Although…
IGS Become Member