Polariscope Guide, Part 1: Testing Gemstone Refraction


Step 3: Practical Gemology

Lesson 12

The polariscope is one of gemology’s simplest and most useful tools. With a little practice and our three-part polariscope guide, you’ll soon be able to conduct some fundamental gem identification tests. You can test gemstone refraction to determine if a gem is singly or doubly refractive, learn the optic figure and sign of a doubly refractive gem, and see gemstone twinning, dichroic colors, and strain.

A polariscope is an inexpensive tool and an essential investment for the gemology student. Read our polariscope review to get a sense of what’s available. You can purchase a polariscope through Amazon or eBay or make one yourself if you follow the instructions below. Even if you purchase a polariscope, knowing how to assemble one will help you understand how the instrument works.

Build Your Own Polariscope

A polariscope consists of three elements: a light source and two pieces of polarizing material, one fixed and one rotating. Almost any light source will do, including good flashlights and desk lamps. Some designs use mirrors to reflect light into the polariscope, eliminating the need for a separate light source. For high quality polarizing filters, look …

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Content Length 2022 words
Reading time 10 min 7 sec

Here's what you get if you unlock this article:

  • Build Your Own Polariscope
    • Types of Polarizing Filters
    • Putting the Filters Together
  • Polariscope Accessories
  • What Is Polarization?
    • Isotropic or Singly Refractive Materials
    • Anisotropic or Doubly Refractive Materials
  • Before You Start: Polariscope Testing Tips For Gemstones
  • Using A Polariscope To Determine Gemstone Refraction
    • If The Stone Stays Dark
    • If The Light In The Stone Changes From Light To Dark
      • Anomalous Double Refraction
      • Testing for ADR
    • If The Stone Stays Light
  • Polariscope Testing Guide Series

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  • Exclusive access to other premium articles and courses
  • Unlimited access to our gem pricing guide
  • Participate in our member-only forums
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