03.01.01 The Refractometer

In this lesson, you will focus on the refractometer, a vital tool for identifying gemstones. Understanding how to effectively use a refractometer is essential, as it helps to determine the refractive index of gems—a unique property that can narrow down their identity significantly. You’ll explore various types of refractometers, including those with built-in lights and external lights, and learn about their common features like the hemisphere, scale, viewing lens, and polarizing filter.

The lesson guides you through the principle of refractive index and its significance in determining how light bends when passing through different materials. You’ll encounter practical demonstrations of how to operate the refractometer, including the important steps of preparing the gem, using the right lighting, and accurately measuring the refractive index. Furthermore, you’ll discover helpful tips for avoiding damage to this sophisticated equipment while ensuring precise readings. Birefringence, or the difference in refractive indices observed in doubly refractive gems, is also discussed, enhancing your ability to identify various gem properties.