Their toxicity requires special handling and working environment, so pay attention to the safety protocols if any of you use them.
Gemstones and Refraction Liquids
by Dr. Raul Berenguel, PhD.
With a high refractive index of 1.741, diiodomethane (methylene iodide) is an excellent refraction liquid for testing sapphires for diffusion treatments as well as viewing their inclusions more clearly. “Blue Sapphire” by Jan-Peter Geringer. Licensed under CC By-SA 4.0.
Table of Contents
Advantages and Disadvantages of Commonly Used Refraction Liquids
Table 1: Properties of Commonly Used Refraction Liquids
Table 2: Hazard Symbol Key
Recommendations
Safety Rules for Refraction Liquids
Partial Immersion Technique
Total Immersion Technique
"Gemologists use liquids with high refractive indices (RI) to ascertain gemstone RIs and, thus, help identify and distinguish them. In addition, any inclusions in a gem may appear more clearly when it’s immersed in one of these liquids. Refraction liquids can also help identify diffusion treatments.
Advantages and Disadvantages of Commonly Used Refraction Liquids
Although quite useful, these refraction liquids have some drawbacks. Gemologists, especially novices, should consider their use carefully. These liquids can be expensive, dangerous, poisonous, and/or flammable. However, less aggressive, less expensive dense oil alternatives do exist. For example, glycerol or glycerin oil has an RI of 1.47.
While other dense oils have desirable RIs, many also have very strong scents. Cleaning a gem dipped in these oils can prove difficult. Another problem you might encounter with these alternatives is a lack of purity. When tested with a refractometer, some allegedly pure oils had RIs so low they could only be dilutions. (Editor’s note: Some natural oils also simply have variable properties, including RIs). As a rule, anytime you use a new refraction liquid in your lab, check a drop of it in your refractometer to confirm its RI before you immerse your gems in it.
Let’s examine the following table of properties of liquids commonly used to test gemstone RIs.
Table 1: Properties of Commonly Used Refraction Liquids ... "
https://www.gemsociety.org/article/gems ... n-liquids/
