ELECTRONIC GEM TESTERS
Several models reviewed
To buy these testers click here
Contents of this page (scroll down or click on these links):
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) or one week (for secondhand items). All the items on this page are new. 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 and has not been maltreated. SETS OF SAMPLE STONES MAY NOT BE RETURNED UNDER ANY CIRCUMSTANCES.
A thermal 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.
ELECTRONIC GEM TESTERS
- PROS AND CONS
The three paragraphs above appear on the page of electronic gem testers in our Autumn 2010 - Spring 2011 mail order catalogue. Electronic 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.
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 moment.
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.
[the Presidium 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
(thermal conductivity) £199.50
Duo Presidium (thermal
conductivity and reflectivity) £239.00
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 is in numerical order, so you can look up the number. The second is 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 reflectivity
Disadvantages of the reflectivity
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 builit-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 take single readings (instead of a few) on successive gemstones, e.g to check several gemstones that are all meant to be 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 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.