Your article on gemstones and refraction liquids has a refractive index list for fluids frequently used in gemstone testing. But many of these are expensive and/or poisonous. Do you have a refractive index list of common household liquids that can be used for immersions? I’ve found information online for things like vegetable oils. Nevertheless, I’d really like to see a definitive, accurate list of “everyday fluids” that actual gemologists actually use. Also, do you have any preferences or tips for using these refraction liquids?
Refractive Index List of Common Household Liquids
|cedar wood oil||1.51|
|cod liver oil||1.46-1.48|
|glycerol (glycerin oil)||1.47|
|rape seed oil||1.47-1.48|
Editor’s Note: This list was compiled from information provided by Donald Clark, CSM IMG, Dr. Gerald Wykoff, Dr. Clive Washington, Roy Kersey, and others.
Vegetable Oil Variations
Be aware that vegetable oils have variable properties. Even oils made from the same species of plant vary in chemical composition depending on things like plant varieties, where the plant grew, how much sun it got, etc. Nevertheless, most plant triglyceride oils (castor, corn, olive, soybean, for example) have fairly similar RIs. Tung oil is a little higher, but make sure it’s not adulterated. Clove oil is quite a bit higher.
Dr. Clive Washington
Maybe it’s not quite a household liquid, but I use a product called Refractol. It’s clear, odorless, nontoxic, and has a listed RI of 1.567. If you buy it online, double check the listed RI. Some product has an RI of 1.52 to make it transparent to glass microscopic slides.
Keep in mind that oils do have variations in RI, and some household liquids, like turpentine, can be noxious.
Donald Clark, CSM IMG
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Cinnamon Oil Pros and Cons
I myself use cinnamon oil. It has a pleasant, if strong, smell. Some warnings: it may eventually eat through the seal of its jar and might produce red welts on you if you get it on your face. (It did to me). Also, if you’re examining rough, some gem dealers may not like you giving them back scented stones. The dealers with whom I’ve done previous business have had no objections to my immersing their rough. Ask first.
Scentless Refractol may be better for some, but cinnamon oil is almost exactly the same RI as tourmaline and topaz. It would be quite good with spinel and corundum, too. Cinnamon oil does have a yellow color, so those who want absolutely clear fluid will have to look for something else.