Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones

We are not new to gemstones. 25+ years experience. We usually test with refractometer, polariscope, spectroscope, etc. but this is portable and customer displayable.It came today and I tested 100 cut stones with 100% accuracy once I calibrated it and got a feel for pressure and 90* angle on the probe. It tested one of my prettiest cut garnets as glass! *^+}{^*! But I put that garnet under the refractometer and it is indeed glass. I hope I didn’t pay much for that rock.This machine tests thermal conductivity. Pretty reliable method to distinguish Glas from precious stone. But; a lot of specimen species have the same thermal conductivity. It’s really good for telling if that ruby ring is a ruby and not garnet or glass. It’s just a starting clue for identifying “what is this random gem?”It calibrates easily. The case isn’t protective enough, especially of the probe. Tools this low price won’t define lab vs natural - need a microscope and skills for that. Overall it’s a great buy at a reasonable price. You don’t become a Graduate Gemologist with one tool but it’s great for buyers, resellers, and collectors to confirm what you’ve got.Easy to use. Performs outstanding. A touch expensive for occasional use. Treat that probe gently, a new on will cost you. Read a book or two if you don’t know that amethyst and citrine are the same mineral species or that sapphire comes in colors.It doesn’t do opal or organics.

I own an auction company and sell many vintage and fine jewelry. This is exactly what I needed to verify my diamonds and gemstones for listings. Easy to use and works great!

Preface: So if you buy this, you need to have a basic knowledge of gemstones. This is not going to be the tester that is definitive if you don’t know anything about gemstones. I am not Certified in anyway, however I have a basic knowledge and this has got me a long way and using this. There are resources that you can look up including a color chart includes to help.As far as the machine itself goes, I am on my second one. I touched my first one with a large charge of Static electricity and I guess it fried it. It was approximately three years old and worked ok- I had to take the results with a grain of salt. It wasn’t very accurate. The second one seems to work better. They have to be calibrated quite frequently so make sure you learn how to do this. The needle will point to a set of gemstones, and it isn’t always the same even with the same stone so it can be a bit finicky and inconsistent on the readings. It is a handy tool to have to determine whether something is glass or gemstone though. It absolutely will not tell you whether something is created or natural.

I reached out to Presidium shortly after purchasing this because it would not *read glass...needle didn't budge one bit after calibration. I was told by other purchasers that this isn't right. I was asked to send video and more explanation (which I did)...after sending their requested information (twice), I never heard from them again. I resolved to thinking that mine just read glass as nothing as it seemed to do okay with other stones. Then, one day I went to use it and it just quit working altogether. After warming up, the needle jumped to diamond and stuck there. It wouldn't make any effort to calibrate or anything. I changed batteries to see if that was the problem. Nope...still nothing. I reached out to the company again but so far have not heard a word back. For as expensive as this machine is....IT SHOULD LAST LONGER THAN 18 MONTHS. I will update this review if I ever get a response from them but as for now, I will not recommend this product at all.

I have been a professional Geologist for over 40 years and this takes the uncertainty out of most gemstones. I do not use the included cord as I don't use the tester it that much. The 2 x AA Alkaline Rayovac batteries last quite a while (not included).I am very impressed. The scale is a bit small for my aged eyes, but that is what reading glasses are for. I believe that the device is made in Turkey and the quality is good. Mine did not come correctly calibrated, but I would have re-calibrated anyway and it is very easy to do. Brief directions are included, or I downloaded the 18 page version from the company website for my alter ego, a professional engineer. It seemed a little pricey, albeit I purchased it anyway. As it works, that is what really counts.I ordered the SmartPro SPGE-I Gem Eye I Gem and Diamond Tester Smart Pro first, but it did not work and they were unable to send a working one after returning it, so I bought this one and had no problems.

I was able to test that one unknown gem that I had was either a diamond or moissanite. It also confirmed that I some of my other gems that I purchased were actually glass! Grr!For some other crystals that I had, they didn't come back as glass. The sapphire was just slightly out of range, but it was close enough for me. The garnet and quartz confirmations were also helpful.The calibration process is a little cumbersome, but after going through the calibration process a couple of times, I eventually got it calibrated.

I purchased this device to be able to determine if gemstones I have are glass (or genuine or lab created). Once calibrated which is easy to do based on the instructions the device works well. Now...it cannot determine if a gemstone is lab created or genuine......but I'm OK with this. Lab created gemstones vs real/genuine ones will have the same chemical composition......especially if the lab created stones are high quality. They will both test the same. What was important for me was to determine if stones that I have now....or purchase.......are glass. The device does this easily. I'm very happy with it!

Pen break easily. No product support that I could find for this issue