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Digital refractometer by Presidium

Digital refractometer by Presidium

Ref: refract-digi-presid

Price: 295.00 Including VAT



We are a UK company offering fast delivery and easy telephone support. Free delivery on this item if paid by bank transfer, see details.

Works with loose stones and also stones mounted in jewellery. The only condition is that there must be a perfectly polished, perfectly flat surface that can rest over the sensor. In practice this means rings and other small items are easy, larger items such as small bangles and bracelets can be fiddly, lumpy items such as elaborate brooches and fancy bangles can be too large to fit.

Can be connected to a computer to see the result on the screen (in addition to the display on the tester), and the computer will display a list of stones that match the reading, which saves you the trouble of having to look them up on a list.


Not only does the software display, on your computer, a list of stones that match the reading, but you can click on each stone to see the other constants, then start working your way through other tests to see exactly what the stone is. This saves time looking up charts (though I still recommend you read one of our books about gemmology!).

It is both lightweight and robust, made by Presidium, the leading manufacturers of gem testing equipment.


This is a reflectivity meter, but clever electronics convert the reading into refractive index. This is the 'standard number' you look up in any book about gemmology or on the internet, it helps identify many hundreds of gemstones.

Range of measurement, 1.000 to 3.000
Power: one 9 Volt battery
Size 5 X 3 X 2 inches (125X 75 X 50mm)
Item weight 150g



USB cable (connects to a computer)

USB mains charger

Laminated card with list of refractive index numbers

Instruction book

CD with software


set of diamond simulants to get more accurate readings (it's ecause they are very high-RI and difficult to distinguishe from diamond), theres a compartment in the tester to house these.


Have you seen the Fascinating article about gem testers? This will answer many questions about electronic gem testers (all electronic gem testers!) - how 'reliable' are they? How 'easy to use' are they?

In summary: no gem tester will light up with a number (or name) that tells you, with 100% certainty, the name of the gemstone. This is because nature does not make gemstones to a standard formulae, there are always variations. All of gemmology is a detective game, starting with an idea of what the gemstone might be (that is what electronic gem testers are for) then using knowledge and skill to find the answer.

If you are new to gemmology, please DO buy this gem tester! - but also buy a good book about gemstones, the best is Gem Identification Made Easy. Not only is this a good guide to gemstones, it also has details of every gem tester, including hints, tips and advanced instructions. For more details of this book, click here - special discount price if you add the book when buying this item