A World of Crystals
We live in a world of crystals. Learn what they are and where you can find them, from deep underground to the dust in the air and even inside our bodies.…
Petalite Value, Price, and Jewelry Information
Gem-quality, colorless, facetable petalite is rare and desirable to collectors. More so if the stones are large and free of inclusions.
Polariscope Guide, Part 3: Testing for Gemstone Twinning, Dichroism, and Crystal Strain
You can use a polariscope to observe gemstone twinning, dichroism, and crystal strain. Test your ability to identify these and other gem properties…
Polariscope Guide, Part 1: Testing Gemstone Refraction
The polariscope is an essential tool for gem identification. Learn how it works, how to use it, and how to test gemstone refraction.
Gem Formation: How are Gemstones Created?
Gem formation usually involves mineral crystallization and other geological processes. Learn how these affect the gemstone properties gemologists…
Gemstone Optical Properties
Learn how gemstone optical properties, like refractive index and pleochroism, help gemologists identify gems and lapidaries choose cuts.
Distinguishing Diamonds: Educating Your Eyes
Distinguishing diamonds from their lookalikes requires educated eyes. Learn what visual features to look for and the properties of many popular…
Parisite Value, Price, and Jewelry Information
More well-known as rare inclusions in emeralds, parisite crystals are usually small and seldom faceted.
IGS Become Member