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Community Member
Posts: 270
Registered: ‎01-30-2007

How accurate is a Presidium Gem Tester?

Anyone own one of these? Is it accurate?

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elias11
Community Member
Posts: 1,490
Registered: ‎06-17-2004

How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Unfortunately, any gem tester will not separate natural gemstones from their synthetic counterparts. (a synthetic sapphire that costs $20.00 will test the same as a natural sapphire that's worth $2,000.00).

In my opinion, these testers have a very limited capability, and are practically useless for positive gem identification.

Elias
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Community Member
Posts: 270
Registered: ‎01-30-2007

How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Thanks Elias

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jewelscollectingdust
Community Member
Posts: 524
Registered: ‎01-08-2010

How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
I think its probably true to say that most gemologists would consider this machine as a rather unconventional tool and bearing this in mind I have had a look at this. I think its true to say the machine does have both advantages and disadvantages. Here are some of my thoughts on it.

Yes it is absolutely true that this device will not seperate natural from synthetic – but I don’t think this is what most people who buy it actually want or expect from it. I think they are looking for something more basic than this.

How many times do you see on this and the other jewellery board questions asking Is my item Gemstone or Glass ? - well it seems this tool is able to give a definitive answer to this question although maybe not provide the specifics - I think that’s what most people are looking for when they buy this.

The machine works by thermal conduction - we all know in an ideal world this isn't the only test used for gemstone analysis but at a rather basic field level for a non-gemologist I can see how it would be useful to have something which will give an indication of which stones would benefit from a more comprehensive assessment and which ones can be automatically ruled out as not so interesting glass. Glass isnt always obvious - it doesnt always show bubbles and some glass can even seem to have inclusions.

In terms of the machines accuracy – well I don’t see much in the way of technical reviews (maybe someone will produce some) so can only go on fairly limited personal experience.
I was very skeptical but interested to see how this responds so tested a small limited range of "known stones" and was rather encouraged to find the machine gave consistently accurate results.
However the reality is that people buy this because they want to use it for “unknown stones” – rather than ones you already know about.

I did find its major drawback is that many stones tested tend to fall into overlapping brackets on the dial - if this is the case there is absolutely no way of knowing whether your item is testing as one thing or the other - only that there are a number of possibilities !.
I must admit even when it indicated a definitive result (where there was no overlap) I have wondered exactly how accurate just taking a simple thermal conductivity reading alone would be ? Maybe someone with technical knowledge can answer this.

So basically I think my opinion is I quite like the tool as a basic indicator and its usefulness at ruling out glass, but beyond this results should be treated with care.

One of the things I do balk about though is the price of this - since we seem to have a few pennies of silicon chip for a few hundred dollars !!

Lastly the only other comment I would make is that this machine is not as hardy as your average diamond tester tool is - although technically it is marketed as portable - my advice would be to treat it gently as you would a high precision instrument - not leave it rattling around in the car or cart it around with you to garage sales !!
I figure you could expect trouble then
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elias11
Community Member
Posts: 1,490
Registered: ‎06-17-2004

How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Good post! Like I said.. these testers have a very limited capability.. ;-)

Elias
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Community Member
Posts: 756
Registered: ‎06-10-2007

How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Their diamond tester is a piece of junk.
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wharper
Community Member
Posts: 9
Registered: ‎06-14-2006

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
To say something is "junk" without further comment is rather simplistic. I own the Mizar diamond tester and I'm quite satisifed that it performs just as advertised.

I've taken to two jewelers whom I know and they've been surprised at the performance, as well.
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lexy143
Community Member
Posts: 6,033
Registered: ‎12-07-2001

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
I've noticed that in the hands of someone who has no experience with jewelry it's a dangerous tool. I've seen many listings described as genuine because their tester said so but it was a stone that had an overlapping ID and the seller, of course, went with the more expensive answer incorrectly.
I've never used one since I deal in mostly silver and semi-precious stones but in the hands of someone with experience it could probably be a useful tool for assistance.
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Community Member
Posts: 2
Registered: ‎07-08-2009

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
These testers are very accurate. However you must remember to keep it calibrated; to make sure it continues to test accurately.
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Community Member
Posts: 2
Registered: ‎07-08-2009

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
These testers are very accurate. However you must remember to keep it calibrated; to make sure it continues to test accurately.

I did not mention if you really do not know Gems, you can still make mistakes using this tester. Example: A zircon is a natural stone, however it will test as a topaz. If you don't know the difference in the appearance of different natural stones, you can still make a mistake using this tester. Another example is a moissenite will test as a diamond. This tester is really good to determine real from glass, but it does have its limits with all natural stones.
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your_babsy
Community Member
Posts: 145
Registered: ‎09-11-2005

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
I have both the Presidium and the diamondnite diamond tester and I have to say I prefer the latter. I find the presidium kinda wishy/washy when testing diamonds. The Diamondnite is clear a beep for yes - simple as that.
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Community Member
Posts: 1
Registered: ‎06-15-2003

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
I agree, this is a wonderful tool in the right hands, but it has to be combined with KNOWLEDGE. Testing colored gemstones is not the simple "Yes/No" answer of the diamond tester.

The more you know about the color and properties of stones, the better. This tester is fabulous for separating glass from everything else, and the easiest way to separate, e.g., aquamarines from blue glass, topaz, or spinel (currently there is no actual synthetic aqua, so this is a reading that does indicate you have a natural stone, unlike the ruby/sapphire reading).

It is also the best, fastest way to detect Victorian doublet or triplet stones, especially when bezel set. The crown will test as garnet, the pavilion as glass, regardless of the color you see.

This tester is invaluable when other methods can't be used -- for example, stones set in icons, statues, book covers, bishops' mitres, and so forth.

Note that as you use it, you will notice that small stones are a little harder to test and will generally fall lower in the bar range (diamonds excepted).

Using this tester will teach you a lot, as long as you are honest and willing to learn from other sources as well. At roughly $200 it's a bargain!
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your_babsy
Community Member
Posts: 145
Registered: ‎09-11-2005

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
This is interesting. I have a pair of earrings with a bright green stone. The loupe and the inclusions suggest a natural stone - maybe a tsavorite but when I test it the Presidium tests as an amethyst. So I am guessing that some things test as in the amethyst range but are really something else. It is the something else that I don't like. So when it is a green stone but tests as an amethyst - what is it?
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Community Member
Posts: 64
Registered: ‎07-13-2007

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Have you calibrated you tester?. Emerald also falls in low part to middle of the amethyst scale on tester.
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your_babsy
Community Member
Posts: 145
Registered: ‎09-11-2005

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
IT does? But the tester has a spot for Emerald. Calibrated ... nope just turned it one and had at 'er.
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arlene_v
Community Member
Posts: 923
Registered: ‎06-09-2006

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
I recently bought a gem tester. Jewellery is my hobby - so for me this is just fun. Can get expensive though!

The main reason I bought one was to distinguish glass from gemstones. And I know that the tester can't tell the difference between natural and man-made - I just want an initial reading, and that being done can decide whether to take it to a gemologist for further assessment.

I have actually found it quite useful - esp. with stones in older jewellery (like garnets etc.) - it is nice for an amateur like myself to have a way of making sure stones are not just pretty glass. :-D

I've also found it quite helpful to distinguish aquamarine from blue topaz.

BUT - the overlapping ranges for the stones provide a challenge for someone who doesn't know too much about gems (that would be me!) - so the competence of the user is vital in making valid judgements. And that being said, they probably don't need a gem tester!
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Community Member
Posts: 46
Registered: ‎12-26-2006

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
Mine paid for itself the first month I had it. A bracelet I thought was glass turned out to be diamond, earrings turned out to be ruby and I had an emerald stick pin I didn't know about. I use it to rule out glass stones, it does that just fine.
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Community Member
Posts: 4
Registered: ‎10-01-2007

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
We've been selling diamond and gemstone testing equipment on and off eBay for many years, in fact - that's all our company is doing and specializing in - selling jewelry testing, measuring and cleaning equipment.

Gold testing and diamond/gemstone testing instruments is 95% of our business.

Here are my thoughts about gemstone identification, Presidium Gem Tester and other related tools, if you allow me:

1. Experienced diamond dealers and gemstone dealers do not need ANY equipment to identify diamonds and gemstones. Most of them also do not have formal education and some of them cannot read, but they are very good at what they do – diamonds and gemstones.

2. GIA graduates are in general definitely more knowledgeable than general public, but GIA Diploma does not guarantee anything, unless graduate is practically involved in diamond/gemstone business and has experience in gemstone or diamond identification

3. Almost 100% of all retail jewelers are very knowledgeable in diamonds (goes for GIA graduates too), but most of them are not good in colored gemstones and could misidentify colored stones easily. Small number of jewelers is really good or even good with colored gemstones.

4. Most jewelers, who are not colored stone dealers, are several levels down from dealers in colored gemstone knowledge.

5. Retail jeweler claiming to have $40,000 worth of gem identification equipment is either rarity or a liar or somebody who paid $10,000 for refractometer. Most gemstones can be identified with $200-1,000 worth of equipment (again, experienced gemstone dealers often only need decent quality 10x jewelers’ loupe).

If you are in need and planning to purchase any gemstone identification equipment you may find the following to be relevant:

1. Traditional equipment – refractometer, spectrometer, polariscope, etc. are all great tools, which would help a lot to identify gemstones, but require studying, knowledge and acquired experience. They may be considered to be the best tools available, but they are useless if you do not know how to properly work with them. May take a lot of time

2. Some traditional tools cannot be replaced with electronic ones – jewelers’ loupe and microscope are good examples. You do not have to have the best of the best, but reasonable optical quality is required.

3. You need to set your expectations right and not expect $200 electronic tester to test for stones, announce guests and brew your coffee (while it is not mowing your lawn).

You need to know limitations of given electronic tester, you need to know what it can and cannot do to be successful in using it. You need to read through instructions and understand how to operate tester properly – I have to admit that some user manuals are not 100% clear for somebody new to electronic testing equipment and may be confusing. If you are in doubt – please contact us and we will guide you through the process.

Here’s some relevant notes about electronic diamond/moissanite/gemstone testers you may find useful:

Diamond testers and Presidium Gem Tester (also Presidium Duo Tester) are using what’s called thermal conductivity test, when heated probe touches the stone and then tester measures dissipation of the heat through the stone being tested.

Thermal conductivity is different for different stones, but some stones may have similar or same thermal conductivity, thus they cannot be distinguished from each other by thermal conductivity testers and further testing using other methods may be needed.

Sometimes common sense may be used to distinguish stones of the same thermal conductivity: some topaz may have very close thermal conductivity to ruby, but you can tell one from another by looking at the stone color, right?

Somebody mentioned that his finger was tested as diamond – ok, assume it was, but here’s the question – was the purpose of the test to trick the tester or to test for diamond?

I hope person testing the finger can tell finger from diamond without testing it…

Somebody mentioned that it cannot tell synthetic stones from real ones – actually – no tester can and most people cannot, many trained people cannot, that’s not a tester’s fault. Synthetic stones (the ones created in the lab, like synthetic ruby, which has same properties as genuine one) are not easy to detect.

Most of the time the only clues are slight structural differences, which may or may not be visible under strong magnification and lack of natural inclusions (better synthetic stone may have those inclusions).
Do not confuse with simulants, which are different stones, which made to look like what they simulate.

Yes, Presidium Gem Tester has many limitations, but for what it does – it is THE ONLY TOOL OF ITS KIND, there is no other tool like it.

It allows you just by touching to tell if sample is piece of glass or diamond, glass or ruby or sapphire, that red stone looking like ruby is actually is a garnet, it will allow you to tell Emerald Vs Jadeite, Topaz Vs Citrine, Topaz Vs Aquamarine, Jadeite Vs Aventurine quartz and more, and it is less than $200 – good enough for “a toy”.

I do not want to write lengthy post, but if anybody would ask about electronic testing tools – I am ready to answer all questions.
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elias11
Community Member
Posts: 1,490
Registered: ‎06-17-2004

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
1." Experienced diamond dealers and gemstone dealers do not need ANY equipment to identify diamonds and gemstones. Most of them also do not have formal education and some of them cannot read, but they are very good at what they do – diamonds and gemstones. "

With all due respect, this statement is inaccurate, to say the least. Even the most experienced dealers cannot separate natural colored gemstones from their better lab-created counterparts without the help of an experienced gemologist - with good gemological equipment - or without the use of the services of a gemological laboratory; this is especially true for identifying expensive gemstones like emeralds and rubies.

Also, many enhancements - for diamonds and colored stones - cannot be detected without good training and good gemological equipment. What good is it for a dealer to be able to identify a diamond or a ruby for example, if he/she cannot identify a potential treatment that could make a huge difference in the value of the stone?

"Somebody mentioned that it cannot tell synthetic stones from real ones – actually – no tester can and most people cannot, many trained people cannot, that’s not a tester’s fault. Synthetic stones (the ones created in the lab, like synthetic ruby, which has same properties as genuine one) are not easy to detect."

I agree. However, an experienced gemologist - with good gemological equipment - has a good chance at separating a natural gemstone from it's lab-created (synthetic) counterpart. With a Presidium Gem Tester, you don't have a prayer!

Elias
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Community Member
Posts: 4
Registered: ‎10-01-2007

Re: How accurate is a Presidium Gem Tester?

in reply to danser4hm7a9r
1." Experienced diamond dealers and gemstone dealers do not need ANY equipment to identify diamonds and gemstones. Most of them also do not have formal education and some of them cannot read, but they are very good at what they do – diamonds and gemstones. "

With all due respect, this statement is inaccurate, to say the least. Even the most experienced dealers cannot separate natural colored gemstones from their better lab-created counterparts without the help of an experienced gemologist - with good gemological equipment - or without the use of the services of a gemological laboratory; this is especially true for identifying expensive gemstones like emeralds and rubies.

Also, many enhancements - for diamonds and colored stones - cannot be detected without good training and good gemological equipment. What good is it for a dealer to be able to identify a diamond or a ruby for example, if he/she cannot identify a potential treatment that could make a huge difference in the value of the stone?

"Somebody mentioned that it cannot tell synthetic stones from real ones – actually – no tester can and most people cannot, many trained people cannot, that’s not a tester’s fault. Synthetic stones (the ones created in the lab, like synthetic ruby, which has same properties as genuine one) are not easy to detect."

I agree. However, an experienced gemologist - with good gemological equipment - has a good chance at separating a natural gemstone from it's lab-created (synthetic) counterpart. With a Presidium Gem Tester, you don't have a prayer!

Elias


1. Elias, I do understand your position, you are a graduated gemologist and it is fine. You need to have value associated with your education and it is fine too. What I am saying is that in most cases experience trumps GIA education and I saw great number of GIA graduates who had no clue. At the same time I am sure that there is a lot of GIA graduates who are very knowledgeable people. GIA label alone is just that - an expensive label. Most diamond and gemstone dealers are NOT GIA graduates.
Here's another though - in most practical situation there is no need in "experienced gemologist - with good gemological equipment" and none is used in day to day buying or selling activities. That said, I must agree, that there are situations requiring lab and expensive equipment involved, in difficult cases or potentially very expensive stones.

In practical life those cases are very small portion of day to day business and mostly GIA is involved to produce GIA diamond certificate as customers like them, as they give them assurance.
Also, experienced diamond or gemstone dealers for sure capable of distinguish most treated stones from untreated.

Speaking about Presidium Gem Tester again and again - its purpose is different from telling synthetics from natural, its purpose is to help in daily task of separating simulants from real stones and if there is any further testing is required to perform it with other tools.

Even graduated gemologist would not use one single test to determine the stone, he or she would back it up with some second test, right?

Why you insist that Presidium Gem Tester should do everything?
It is just another test, like testing refractive index or hardness.
It works perfect when it is understood properly.
Again, it is not an universal all inclusive gem testing tool, but please give me an example of such universal tester - electronic, optical or any other.
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