Using a Reticle: A Guide for Gemologists
Step 4: Gem Grading
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.
General Reticle Techniques
The following instructions are for using contact reticles with a microscope. Using them with a loupe …
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- What is a Reticle?
- General Reticle Techniques
- Reading to the Hundredth of a Millimeter
- Measuring Gem Lengths with a Reticle
- Table Width
- Star Percentage
- Measuring Gem Angles with a Reticle
- Crown Angle
- Pavilion Angle
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