ELECTRONIC GEM TESTERS
Several models reviewed
(also downloads, includes instruction manuals)
THIS ARTICLE: CONTENTS
There is no machine that will simply light up with the name of a gemstone; there is no machine that will distinguish natural stones (grown in the ground by nature) from synthetic (grown in the laboratory by man, using the same chemicals and the same conditions found in nature) – not to be confused with imitations, where one stone imitates another. Gem testers merely suggest possibilities and you must use a combination of experience and other tests to come to a conclusion. Too complicated? Then do not buy a gem tester! Sounds interesting? Then you are about to discover a fascinating world of optics, chemistry, and how to become a super-detective in the quest to identify gemstones.
You may return any gemtester bought by mail if you are not satisfied, providing this is done within two weeks (for new items..all the items on this page are new) or one week (for secondhand items). SETS OF SAMPLE STONES MAY NOT BE RETURNED.
meter shows several common gemstones (see the picture of the
meter below). It is easy to use on both loose stones and stones mounted
in jewellery. It cannot distinguish diamond from Moissanite (a man-made
stone). It is best for suggesting what a stone isn't e.g. it might be
glass but it can’t possibly be sapphire.
GEM TESTERS - PROS AND CONS
Some examples of where these testers are of most use:
- you have been given
a parcel of stones and want to sort those that are 'interesting' and worthy
of further investigation from those that can be put to one side for the
Some examples of where these testers are of least use:
- you are quite happy
to work slowly and carefully in laboratory-clean conditions, but you must
have a machine that will positively identify any stone.
Here are some independent evaluations from two internet forums run by gemmologists. Gemmologists are scientists, they are not interested in sales hype:
Just this morning some students and me have been checking the digital refractometer. In this case we tried to find out if a stone purchased on internet was indeed a GGG or a CZ. This reflectivity meter worked (in this case). The result was proven by its SG.
Duo] is good for quick sampling, but you do need to keep it calibrated
with known samples. I also haven't been able to get it to work reliably
with tiny stones. Relying on any one characteristic to identify a material
practically guarantees misidentification.
Standard Presidium (thermal conductivity) £195.00
Duo Presidium (thermal conductivity and reflectivity) £289.00
The 'thermal' part of the tester (with the scale that shows the names of the stones) is identical to the standard model, above, so see above for pros and cons.
In addition, it has a reflectivity meter. This gives the result as a number which you look up on a chart. The chart includes 76 common gemstones, and we include two versions of the same chart, the first in numerical order (so you can look up the reading), the second in alphabetical order of gemstone (so if you already have a good idea as to what the stone is, you can see how closely the reading on the machine matches it).
Advantages of the
Disadvantages of the
Digital Refractometer £329.00
All the pros and cons of a the reflectivity meter in the Duo, above, apply to the digital refractometer too. But there is one big difference. The number it displays is refractive index, the standard number every gemmologist understands, the number you can look up on any standard reference chart, the number that will help identify many hundreds of gemstones.
Easy to use, and the result is displayed within one second. The only condition (as with all these machines) is that the stone must have a perfectly polished flat surface that covers the sensor. That includes stones mounted in jewellery (unless the item -cut stones (they're not flat) and not stones in large and lumpy jewellery that won't fit.
As I have said many times above, there is no machine that will simply 'positively identify' any gemstone - but if you are serious about being able to identify hundreds of gemstones, this is by far the best and, in my opinion, well-worth the extra money.