Using a Reticle: A Guide for Gemologists

Step 4: Gem Grading

Lesson 11

reticle - 20x magnification

What is a Reticle?

A reticle (réttik’l) is an optical device used in conjunction with a magnifying lens. For example, the cross hairs on a gun sight are a type of reticle. Machinists use reticles with a variety of micro-rulers and micro-protractors for fine measurements. While not specifically designed for gemology, these can serve gemologists very well.

There are two types of reticles: contact and non-contact.

  • Microscope eye pieces incorporate non-contact reticles. They have the singular advantage of being always in focus and the disadvantage of being the most expensive.
  • The viewer places contact reticles directly on the object being measured. These cost considerably less than the non-contact type and are available individually or in sets.

Since your needs will vary, a combination of reticles is best.

Contact reticles come unattached. You can use them with any loupe or microscope. Others attach to a special hand loupe. These are almost useless for measuring things like the pavilion angle, where the part being measured is not directly in contact with the scale.

reticle - varieties

General Reticle Techniques

The following instructions are for using contact reticles with a microscope. Using them with a loupe …

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Content Length 1609 words
Reading time 8 min 3 sec

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

  • What is a Reticle?
  • General Reticle Techniques
    • Reading to the Hundredth of a Millimeter
  • Measuring Gem Lengths with a Reticle
    • Table Width
    • Star Percentage
    • Half-Lengths
  • Measuring Gem Angles with a Reticle
    • Crown Angle
    • Pavilion Angle

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