Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones
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Availability:
In Stock.
Arrives
Wednesday, Apr 22
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Color: Presidium Gem Tester Complete Unit
Features
- INCLUDED ASSISTED THERMAL CALIBRATION | Now easily self calibrate your device to your testing environment
- INDUSTRIES MOST TRUSTED | Gemstone tester redesigned to be more compact, sturdy and portable
- THINNEST RETRACTABLE PROBE TIP I PGT II features the industrys thinnest retractable probe tip
- VERSATILE AND RELIABLE | Consistent and reliable results every time. Identifies diamonds/moissanites
- SIMPLE & EASY TO USE | Clear and easy-to-read analog dial; Can differentiate 16 types of gemstones. IMPORTANT TO NOTE | The calibration of this product may be affected during shipping. If you experience issues with calibration, please reach out to the seller for assistance prior to returning the item.
Brand: Presidium
Power Source: Battery Powered
Style: Compact
Color: Presidium Gem Tester Complete Unit
Item dimensions L x W x H: 7.8 x 4.5 x 3.8 inches
Power Source: Battery Powered
Upper Temperature Rating: 51 Degrees Celsius
Measurement Type: Thermoelectric probe
Style Name: Compact
Color: Presidium Gem Tester Complete Unit
Item Dimensions: 7.8 x 4.5 x 3.8 inches
Brand Name: Presidium
Model: PGT-II
UPC: 798804941239 730792705646
Manufacturer: Presidium
Item Type Name: PGT II
Unit Count: 1.0 Count
Warranty Description: Please contact the seller directly for warranty information for this product. You may also be able to find warranty information on the manufacturer’s website.
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Wednesday, Apr 22
Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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Top Amazon Reviews
Color: Presidium Gem Tester Complete Unit
A neat tool to have in checking for diamonds (and some other stones) but hard to read between some types of gems as the identification bands overlap. It is, however, VERY good at diamond testing and if you have some knowledge of gemology it is helpful in testing other stones as well. Very good at ID-ing glass and plastic, so it is good to have for that alone when looking at old costume stuff. Calibration is easily accomplished and it holds for several operations. Battery life is sufficient for a days worth of flea-marketing.
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Reviewed in the United States on March 19, 2026 by Keith
Color: Presidium Gem Tester Complete Unit
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.
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Reviewed in the United States on June 20, 2024 by Betty Turner
Color: Presidium Gem Tester Complete Unit
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.
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Reviewed in the United States on September 19, 2024 by San Jose Reviewer
Color: Presidium Gem Tester Complete Unit
The media could not be loaded. UGH!! I am appalled at the amount of money I spent on this, only for it to stop working after a few uses. The unit flashes a red light, & the needle moves to the diamond area & stays there. It will not budge no matter what I do, unless I unplug it. When I plug it back it, after the red light stops blinking, the needles goes right back to diamond area and won't move. I am so disgusted at this faulty product I was sent.
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Reviewed in the United States on February 5, 2026 by Genevieve Grosvenor
Color: Presidium Gem Tester Complete Unit
We were concerned about it's accuracy based on some of the reviews. We've had no major issues. We found it a good tool to help confirm other numbers you've gathered. It calibrated right out of the box. Read the instructions. It wants at least two calibration passes and sometimes the glass calibration test seems to drag on a bit longer than it does for the generic calibration side. It's a minute or two total, be patient. Don't test the same stone over and over. If testing loose stones buy the metal testing plate. If you are a jeweler a round bezel block works great. They work as a heat sink so your hands don't warm the stone and alter the result. Our only issue we've seen once was about two hours into the sorting marathon of larger stones with similar SG values that we believed were mostly quartz varietals. The results started being all over the board and didn't match up to common stones. Took us three stones that we moved off to the side for extra testing before we realized it had drifted. A known amethyst cabochon we had tested earlier was testing wrong. A two minute calibration and all was fixed. We tested it on a few known stones we had purchased from reputable US dealers and they all popped up as expected if they were of the testable types. This will help you narrow down your choices but for many stones by itself it is not good enough. If you have a pale blueish stone it could meter and hit the bars for tourmaline, amethyst and aquamarine on the right side of the indicators. All of these can come in very pale coloration of a similar ballpark. You would need SG and/or RI numbers to pick out which type it is. We used it to help sort out about 500ct of mixed stones. Since we knew the vague ten primary types of semiprecious stones that were in the mix sorting by color and then spot checking worked out well. Larger stones we were going to set into pendants or rings got double checked with RI and SG readings. It also helped identify a few nice odd balls that were in the lot. Gave us a class of gem to look into. For example Topaz comes in a wide range of colors. Something popping up on the Spinel and Topaz range lets us isolate what other identifiers we need to be looking at to identify it. In that case the RI should isolate which stone it actually is. If it came up Spinel I could further verify by checking the color against an expected SG for that specific color. For identifying the common sold gems often used in rings and necklaces I think it does a good job without any extra tools needed. If you were going to use it a lot I would consider buying a small cabochon or two from a US supplier. A quartz one like Citrine or Amethyst and a cheap clear topaz. Then you have known stones to test if you start getting weird results. If they test off, then you just recalibrate. If it doesn't move it's usually acrylic or a plastic. If you intend to sort gem lots and such you will need some extra testing tools to go along with this.
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Reviewed in the United States on May 12, 2023 by James D
Color: Presidium Gem Tester Complete Unit
I love this tester and it's easy to use. I am well aware of how delicate the tester point is, so I am VERY careful with it and keep the tip cover on when not in use. This is a great item to have on hand. You can test all the gems you're unsure about... and do the same for your friends. It comes in a nice case and is easy to store. I had a tester for decades before this one, but it just tested diamonds. This one does so much more and the price is so reasonable. Treated right, you will have it for years and years. AND... it's so easy to use!
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Reviewed in the United States on January 9, 2026 by L. Vandeveer