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). But you may not return an electronic gem tester after that time merely because it is 'too complicated' or 'not consistent' or you are 'not happy with its readings'. Unless, of course, it is quite obviously broken and is still under guarantee. SETS OF SAMPLE STONES MAY NOT BE RETURNED UNDER ANY CIRCUMSTANCES.
Although these warnings seem somewhat severe, gem testers aren't really that bad! I'm merely trying to frighten away the many customers who will buy these thinking they get instant and 'reliable' answers, they will be disappointed and I don't want my customers to be disappointed.
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 'Gem-n-Eye'. 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) £199.50
Duo Presidium (thermal conductivity and reflectivity) £329.00
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
Gem-n-Eye (reflectivity) £349.00
All the pros and cons of a the reflectivity meter in the Duo, above, apply to the Gem-n-Eye too. But there is one big difference. The built-in computer database gives you the result as names of actual gemstones rather a number you have to look up on a chart. And it will list all the stones that could apply to the reading. Cleverer still, you can set it to show the most common gemstones, uncommon gemstones, or very rare gemstones, so that you are not bombarded with obscure names. There is also a 'quick' setting so that you can quickly take readings on successive gemstones, just to check that they are all the same.
Once you have narrowed down the possibilities, you can call up each gemstone for more information, nine gem constants including RI (refractive index), BI (birefringence), SG (specific gravity) and crystal system. If you don't understand all that, you may find it useful just to look at the list of Colours to see the colours in which the stone is found. In this way, the Gem-n-Eye not only gives you the most important number (refractive index) but suggests what you should look for next. You can also work the system backwards, by looking up the name of a gemstone and seeing all its characteristics.
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.