Alternative Birthstones
Not happy with your birthstone? Explore these alternative birthstones associated with astrological signs, angels, the hour or day of your birth,…
Table of Refractive Indices and Double Refraction of Selected Gems
Refractive indices and double refraction (birefringence) help gemologists identify gems. The following table lists these values for selected…
The Physical Properties of Gemstones
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,…
Identifying Synthetic Gems
Distinguishing natural from synthetic gems is a critical skill for gemologists. It could mean the difference between valuing a gemstone at thousands…
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…
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…
Destructive Gemstone Tests: Acid Testing
In some cases, a hot point test won’t distinguish plastic simulants from natural gems. Some plastics release a protein smell when hot point…
Destructive Gemstone Tests: Dye Testing
Gems are frequently dyed to enhance their color. Distinguishing natural from enhanced stones is an essential skill for gemologists. The materials…
Refractometer Guide, Part 3: Determining Optic Character and Recognizing Optic Effects
Step 3: Practical Gemology Lesson 6 Back to syllabus Optic character is another useful clue in gem identification. This property exists in every…
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