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Community Member
Posts: 1
Registered: ‎04-11-2015

Re: How accurate is a Presidium Gem Tester?

in reply to brunosfinejewelry

I found a nice looking rock once.  It looked like a diamond but it was too clear for me to feel comfortable.  I was going to put it back because I couldn't find an inclusion under magnification even though I simply loved it's sparkle.  I'd never seen anything, not even zarconia, sparkle like that rock in my life though so I thought I'd take another look.  Nothing sparkled like that rock in the sunlight. two different types of stone testers consistently said it was a diamond and when I tried to fog it up it would be gone in a second, it scratched glass (not that it matters much, a lot of stones scratch glass).  I increased the magnification to be sure from 8 to 16 and looked again, I looked through every facet and found an inclusion and the likely source of the unusually brilliant sparkle other than it's nice symmetry and the way the faces line up so well with each other.  There was an extremely fine line of silk in the bottom of that 1 ct stone that went almost all the way across the bottom.  I left it there and thought about it and did some more research, he wanted a pretty penny for the stone in my opinion for something his IGS certificate said was just an H, although I think it might be a bit closer to F; maybe a G but I am not completely sure.  It was a loose stone so I bought it, I'm not sure what I'm going to do with it yet, I'll probably put it in a ring, for now it's just a loose stone.  I picked up two half carat supposed blue diamonds from the same guy, they looked good and I thought I'd have them placed beside the white diamond some day.  I'm not sure if I'll ever get them mounted or what I'll put them in.  I was just looking for some colored stones when I walked in, I don't normally deal with diamonds because there are too many fakes but I loved that stone's sparkle and fire, when it's being moved the sparkle can blind you with dazzaling colors, mostly orange, red, and yellow but there was a little blue and red if I remember right.  I don't remember seeing any green and I don't really remmeber hardly any blut, all I can remember for the most part is red, yellow, and orange.  I'll have to take a look at it again some sunny day. 

Community Member
Posts: 661
Registered: ‎11-15-2004

Re: How accurate is a Presidium Gem Tester?

in reply to brunosfinejewelry

HITH does anyone synthesize a stone w/o creating it in a lab?

 

It's a common error. People confuse synthetics with *imitations*. Synthetics are always lab. Imitations, often but not always so - such as rock crystal being a diamond imitator. S'why it's sometimes known as "Herkimer diamond."

 

 

Community Member
Posts: 2
Registered: ‎08-13-2009

Re: How accurate is a Presidium Gem Tester?

in reply to rixstuff
Synthetic is not Lab-Created. Labs have the same properties as a genuine mined gem.
Community Member
Posts: 2
Registered: ‎08-13-2009

Re: How accurate is a Presidium Gem Tester?

in reply to bojibelle

If it looks too good to be true - it probably is. Too Sparkly, Too White, etc. Only a trained eye can tell if it is a diamond. Someone who looks as diamonds often enough can tell. Refraction, inclusions, cloudiness, etc. Even a Moisonite tester is not 100%. Machine Testers are nice but donot take the place of the trained eye which takes a long time to truely develop. No GIA course in the world can teach you fully. This is where experience & viewing gems regularly can only truely teach. So Machines & Book Courses are great only for guides. Experience can't be beat.

Community Member
Posts: 711
Registered: ‎01-11-2009

Re: How accurate is a Presidium Gem Tester?

in reply to minini1

minini1 wrote:
There is no accurate gem tester on the market. The only way to use them is in reverse, eg. if it says gem is genuine, it is not and vise versa. I have had clients call me crying saying they were told all their diamonds from heirlooms & wedding ring were fake. I asked them how were they tested, they said with a diamond tester at the jewelers. They drove 100 miles to show me the jewelry and they were all genuine, nice diamonds. As soon as they told me that I told them they're all real and no "jeweler" would have one of those a mall jewelry store might. Recently also had a lady bring me in her pot metal watch encrusted with glass foilbacks which they were told by a fake jeweler they were real. Happened more times than I can remember.

 

 

I agree that these type of testers are not fail safe. I will say that most of the issues you are describing are not common and usually caused by ignorance, abused or old well used testers, bad eyesight or even customers that like to make up stuff. When not abused or overused these testers will get it right most of the time.  As far as the Moissanite testing goes, If you can't tell the difference without one you should not be assessing one anyway.  I am curious to see what happens when more of the new man made Diamonds hit the market.   

___________________________________________________
Some should name the chip that resides on their shoulder "Hypocrite"
Community Member
Posts: 15
Registered: ‎10-08-2007

Re: How accurate is a Presidium Gem Tester?

in reply to finerflavorantiques
Yes those instruments are scientific and work. The gem testers talked about here are about as scientific as using a stick to find water. Sometimes you'll get correct reading and even a blind squirrel finds an acorn once in a while. Is GIA still offering the mail order course where they send you the work books with the answers in the back?
Community Member
Posts: 15
Registered: ‎10-08-2007

Re: How accurate is a Presidium Gem Tester?

in reply to bojibelle
There is no accurate gem tester on the market. The only way to use them is in reverse, eg. if it says gem is genuine, it is not and vise versa. I have had clients call me crying saying they were told all their diamonds from heirlooms & wedding ring were fake. I asked them how were they tested, they said with a diamond tester at the jewelers. They drove 100 miles to show me the jewelry and they were all genuine, nice diamonds. As soon as they told me that I told them they're all real and no "jeweler" would have one of those a mall jewelry store might. Recently also had a lady bring me in her pot metal watch encrusted with glass foilbacks which they were told by a fake jeweler they were real. Happened more times than I can remember.
Community Member
Posts: 4
Registered: ‎05-11-2012

Re: How accurate is a Presidium Gem Tester?

in reply to finerflavorantiques

excuse me - a spectrometer and or refractometer

Community Member
Posts: 4
Registered: ‎05-11-2012

Re: How accurate is a Presidium Gem Tester?

in reply to vintage-memories

As with all gem testing there should usually be more than method employed when determining the stone - you can use this in conjunction with a spectrometer and also there is the magnet water test - as synthetics do not have added iron as of yet.

Community Member
Posts: 4
Registered: ‎05-11-2012

Re: How accurate is a Presidium Gem Tester?

in reply to carols5294

No - actually it doesn't differentiate betweeen moissanite - that is the one that it will not - and you have to have a seperate moissanite detector. As stated per the owners manual. No thermal tester will differentiate between diamond and moissanit.  http://presidium.com.sg/Userhandbook_19062014/Userhandbook_PGT_Presidium_Gem_Tester.pdf

Community Member
Posts: 661
Registered: ‎11-15-2004

Re: How accurate is a Presidium Gem Tester?

in reply to bojibelle

I knew I was exhausted so I didn't want to touch it either.

Community Member
Posts: 1,198
Registered: ‎08-03-2004

Re: How accurate is a Presidium Gem Tester?

in reply to bwrighttwo

bwrighttwo wrote:

carols5294 wrote:

.  Lab created gemstones are identical to natural gemstones in every way except they are flawless.  That's the only way a gemologist can tell the difference in lab-grown and natural.


Uh Oh......Hanging curve ball.  Can't wait to see who jumps on this.


I'm not touching it.  I've tried way to many times to explain natural, synthetic, lab-created and simulated and what the tester will and won't test.

Community Member
Posts: 711
Registered: ‎01-11-2009

Re: How accurate is a Presidium Gem Tester?

in reply to carols5294

carols5294 wrote:

.  Lab created gemstones are identical to natural gemstones in every way except they are flawless.  That's the only way a gemologist can tell the difference in lab-grown and natural.


Uh Oh......Hanging curve ball.  Can't wait to see who jumps on this.

___________________________________________________
Some should name the chip that resides on their shoulder "Hypocrite"
Community Member
Posts: 4
Registered: ‎05-14-2005

Re: How accurate is a Presidium Gem Tester?

in reply to elias11

This tester will tell you if a stone is a diamond or Moissinate but none in this price range will tell you the difference between the two.  You will also get a slightly lower reading for sapphire, ruby or emerald.  I use one very frequently and it's reliable if you calibrate it properly.  If a stone is synthetic, you will not get a reading or signal.  If it's natural or lab-grown, you will get a signal.  Lab created gemstones are identical to natural gemstones in every way except they are flawless.  That's the only way a gemologist can tell the difference in lab-grown and natural.

Community Member
Posts: 1,198
Registered: ‎08-03-2004

Re: How accurate is a Presidium Gem Tester?

in reply to vintage-memories

vintage-memories wrote:

Can you suggest how to keep it calibrated, please.


Read the directions

Community Member
Posts: 7
Registered: ‎04-19-2006

Re: How accurate is a Presidium Gem Tester?

I enjoyed your explanation... I'll give my tester another try. Thanks.
Community Member
Posts: 7
Registered: ‎04-19-2006

Re: How accurate is a Presidium Gem Tester?

in reply to pan2roc

Can you suggest how to keep it calibrated, please.

Community Member
Posts: 7
Registered: ‎04-19-2006

Re: How accurate is a Presidium Gem Tester?

in reply to elias11

When I purchased my gem tester and first used it I was very dissapointed.  The only good reading I got was on the diamonds.  Also, it identified "glass", which was helpful. I did not realized it detected synthetic stones.  I am thinking of selling it and I'm sure I will not get the same price I paid for it...too bad...I should have researched it a little better. 

Community Member
Posts: 7
Registered: ‎04-19-2006

Re: How accurate is a Presidium Gem Tester?

in reply to wharper

I use the MIZAR diamond tester and like it very well.  I have had it for ages and always carry it in my purse.  One never knows when one will have the opportunity to see some "gems" and hope they are diamonds. I use mine all the time

Community Member
Posts: 1,198
Registered: ‎08-03-2004

Re: How accurate is a Presidium Gem Tester?

in reply to bclear0693

No, they do not have a test rating for opal.