Presidium Gem Tester

[CharmyPoo]

Does the Presidium Gem Tester or other refractometer instruments identify natural versus synethic stones?

I purchased some stones (not expensive but not dirt cheap). The seller insist they are natural because she tested them with the presidium gem tester. I thought that it identified the stone species but not if it is natural or synethic.

Thoughts?

 

[T L]

Date: 4/28/2010 11:00:09 PM
Author:CharmyPoo
Does the Presidium Gem Tester or other refractometer instruments identify natural versus synethic stones?


I purchased some stones (not expensive but not dirt cheap). The seller insist they are natural because she tested them with the presidium gem tester. I thought that it identified the stone species but not if it is natural or synethic.


Thoughts?

There are some gems that you cannot detect as synthetic without highly expensive lab equipment, so to say that a gem tester can identify any synthetic stone is incorrect.

What kind of gems is she talking about?

Here is a snippet of information about this tester that I obtained from a more scientific web page. I cannot say where I got this information unfortunately.


This tester is a thermal conductivity tester and is a further development
(I hope ) of the thermal conductivity tester designed to differentiate diamonds from everyting else (except they dont work to distinguish moissanite , a relatively recent development) When I saw a picture of this instrument with labels for various types of stones I thought it might be a good idea and hope to play with one of these before too long.

That said using such an instrument can/should only provide an indication of what a stone might be. Other than the above,, thermal conductivity measurements have been qualitative rather than quantitative. Also such measurements are likely to be very dependent on the temperature of the specimen , the ambient temperature, the state of the units batteries, possibly the recent measurement history of the probe or the stone or both , and how hard and consistently you press the probe onto the stone,, to name a few that I can think of.

If I had one of these instruments I would develop a set of check stones or pieces. Different types of glass, different faceted stones perhaps a ball bearing or two. Put them in a medicine vial in the fridge and test them starting at a constant temperature and see if the instrument doesnt behave a bit more consistently. I hope it does because I think it is a good idea.

But it is not a first line ID instrument and at this time you couldnt mention results from it in a courtroom for example. Just something to help confirm a trend or suspicion in other data.

 

[lelser]

Date: 4/28/2010 11:00:09 PM
Author:CharmyPoo
Does the Presidium Gem Tester or other refractometer instruments identify natural versus synethic stones?


I purchased some stones (not expensive but not dirt cheap). The seller insist they are natural because she tested them with the presidium gem tester. I thought that it identified the stone species but not if it is natural or synethic.


Thoughts?

It won''t help with a natural/synthetic separation at all. Not even a little bit.

I own and use a Gem Meter II and it''s a damn handy tool, especially for rough material where I can''t get an RI. It will tell you that the "sapphire" isn''t corundum, but will only give you a likely range of things it might otherwise be.

The whole point of synthetic stones is that they are chemically identical to the natural ones. Same RI, same SG, same thermal properties. Sometimes there are trace elements that differ and a spectral reading will help, or one may react to UV light, but the best way to tell synth from natural is usually a trained gemologist with a microscope.

If the seller thinks she can tell natural from synthetic based on a thermal tester, you should seriously re-consider spending money with her. At least take the stones to a lab before the inspection period is over.

Cheers,

Lisa

 

[LD]

I own one. If for example you''re testing a sapphire it may either register as corrundum (good but not conclusive) or it may register as something else, in which case it''s another gem (or synthetic). So it can help you to narrow things done but not so that you can be 100% sure.

 

[chrono]

I would never rely solely on it; the purpose of the tester is to be used as one among many other tools to help narrow down what the stone isn’t, not necessarily to have a definitive answer as to what the stone is. It will help in determining if the stone is of a certain species but not tell you if it is natural or a synthetic.

 

[ruffysdad]

Date: 4/28/2010 11:00:09 PM
Author:CharmyPoo
Does the Presidium Gem Tester or other refractometer instruments identify natural versus synethic stones?

I purchased some stones (not expensive but not dirt cheap). The seller insist they are natural because she tested them with the presidium gem tester. I thought that it identified the stone species but not if it is natural or synethic.

Thoughts?

Natural sapphire and ruby are aluminum oxide and the same''s true for either the cheap split boule, flame fusion ones and lab grown hydrothermal flux ones. Therefore, they''ll test identical. That''s just one example and there are a lot of others. I''d take a big step back and think this one over as I see red flags all over it. There''s still no substitute for knowledge backed up with a well trained eye.

 

[enbcfsobe]

Even the goodwill people state on their site that the Presidium tester cannot distinguish between natural and synthetics. I would be very wary of dealing with this person.

 

[lelser]

Date: 4/29/2010 6:32:40 AM
Author: LovingDiamonds
I own one. If for example you''re testing a sapphire it may either register as corrundum (good but not conclusive) or it may register as something else, in which case it''s another gem (or synthetic). So it can help you to narrow things done but not so that you can be 100% sure.

It will register as corundum whether it''s natural or synthetic corundum. Synthetics read identically to natural stones on thermal testers and refractometers.

Cheers,

Lisa

 

[CharmyPoo]

Thank you all - confirmed what I thought. These sellers ... geez.