Does anyone have experience with digital refractometers? RE their accuracy and best brand? I am needing one to complete the IGS Gemmology course.
Even GIA only requires the same type of refractometer that’s been used since the 1880s. They are just in newer cases these days and you really should learn to use it, to see shade cutoffs and learn to calculate birefringence. High tech toys are nice…but the industry standard is the standard RI Liquid and Hemi cylinder Refractometer. Good luck with your tests.
I failed the test and the hardest part was the refractometer. I’m taking the test again and am determined to conquer the refractometer, have new fluid and batteries so hope that helps.
Do you have a monochromatic light source in addition to your white light?
The digital refractometers are useless for gemological identification. I also was wondering and thinking about them and then I started to do some research and studyies about them and I now I can’t remember why they were useless… if I remember correctly it was because you could only find one reading, and not the high and low readings, so they are basically useless…
Not all digital refractometers are bad. I purchased a Jemeter Digital 90. Like anything else it takes practice with your equipment. You can get hi low readings by slightly moving the gem over the eye. I take 4 readings per stone, and I use the highest and lowest numbers.
I still think the manual method yields more accurate result more consistently. It just takes longer. There is a reason the method hasn’t changed. With the Jemeter I get readings that are off by small amounts, because the gem must be completely clean. Any, and I mean any, residue will throw results. You will also get crazy results if the gem is not large enough or if it’s not faceted completely flat. Light escaping edges is an issue since air has its own RI 1.000277, and you can’t can’t calculate that for that in your results.
Remember the refractometer is just one method on your check list. I suggest you question the advertising on digital models. They most likely have stones the know will show the perfect number. Calibration can be hard.
Hello … Since I have taken the IGS practical exam on Gem Identification and passed it, I know how difficult it is. Before I was a Gemologist, I was a certified Metrologist (science of measurement for the military), so I’m real good with all kinds of measuring equipment. I have a Gem-n-Eye Digital Refractometer and find it is very good at detecting GLASS stones and also confirming when an RI is OTL (Over The Limit) of 1.81 on the standard refractometers. It is my learned opinion that you will have great difficulty in passing the IGS practical exam by only using a digital refractometer. However, it is very useful to have and use both types.