Review - Duplex II and Rayner Dialdex Refractometers
Review - Duplex II and Rayner Dialdex Refractometers

Product Review: Duplex II and Rayner Dialdex Refractometers


The Duplex II and Rayner Dialdex both make excellent refractometers for gemologists. How do they compare head-to-head? Learn more from our review.

3 Minute Read

While reviewing "no name" refractometers, I read that the Duplex II is the only refractometer designed specifically for spot readings. As I discovered, the "no name" brand units were almost useless at spot readings. I was left wondering how much their smaller size had to do with that.

As an experiment, I purchased a Rayner Dialdex. It's considerably smaller than the Duplex II and about the same size as a "no name" brand. Both of these instruments are expensive. New, the Duplex sells for around $625. (Editor's note: You can find used Duplex II and Dialdex refractometers for sale online at lower prices).

How do they compare?

Ease of Use

At first, I found the Rayner Dialdex very awkward to use. However, I soon got comfortable with it. In fact, I remembered I also found the Duplex II awkward at first. So, this one is a tie.

Polarizing Filter

One of the first things I noticed about the Dialdex was the polarizing filter. It made the display much darker and noticeably harder to read. I learned to take it off, except for those occasions when I actually needed it. The filter on the Duplex II never...


Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

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