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

I have only owned this tester for less than a month. So we'll see how things go over time. I haven't had any issues yet with the calibration (knocking wood). If you buy this, make sure to register your product right away so you can get assistance if your tester isn't performing as it should. I'm fairly inexperienced when it comes to gemstones, but I sell vintage jewelry (mostly costume) so I do come across items I need to identify from time to time. Honestly for someone like me, it's actually just great to be able to test older pieces and confirm whether I'm dealing with glass or a gemstone. I consider the tester to be a starting point for additional research, not necessarily the final word. I was pleasantly surprised to identify some pieces I own that I hadn't really assumed to be gemstones, or just didn't have a clue about the specific stone. But I can see the more likely scenario is that it will identify a stone as something like quartz, then I have to go do my research because that can encompass multiple varieties of stones. So if you consider this as a research tool and understand that you still have to go out and learn more information, this is a pretty good investment and will probably end up paying for itself.

This works well at identifying many gems. Some of the answers are a bit arbitrary falling in between one gem or another. For the money, I expected something to feel a little bit more substantial and this is quite lightweight but it does seem to work well.

Going through vintage jewelry this product is a must! It sure helps you correctly identify your stones. I love it.

Not well made. It worked reasonably well, although readings were somewhat inconsistent. It was a decent first screening tool. Then one day, after very limited use, the needle stopped moving. Almost $300 wasted! Buy something else!

Bought this for my wife to use to check out all her jewelry. She discovered one piece is not a gem but colored glass! It took us a couple of times to calibrate it, but we did it successfully. Not sure what these kinds of things should cost, but it seems overpriced to me... but it's a supposed precision instrument so maybe it's not overpriced. It's certainly not industrial grade equipment, but good for the jewelry collector/reseller/buyer. Comes with a nice case. Seems to be more accurate and capable than the pens you can buy for a lot less money.

Have had this for a while now, still working perfect.

Tried 4 times of calibration, and it never reached CAL area, but it detect Glass right all the time. Tried on very expensive RUBY, it worked. Tried on cheaper opaque ruby, it didn't work. Tried on Topaz, it worked. Tried on Diamond and Moissanite, it worked. So even though calibration is not perfect, it works, anyhow. But really, need to improve calibration features as lots of review says failure of calibration.

This is an easy to use tester. It is very accurate too. Easy to use. It was a little pricey but it all depends on if you want accuracy or not. I believe this is an accurate measure and trust worthy. b I recommend this item if you are testing gems.

Testing

The presidium instrument gemstones tester is a good product. It would have been great if there where actual light to indicate the name of the exact stone instated of just a line with more the one name leaving you to guess what exactly it's.

I like the variation this tester has for identifying various gems . However , I find the pen has been extremely finicky and I can hardly have it calibrate up to the Cal indicator level without constantly cleaning and wiping down the cal glass and pen tip. I may have received a faulty pen as it has play back and forth ?

This tester was broken, I only wasted time on waiting for it and the returning it.

The categories are vague so follow up research is definitely needed. I tested a large 100% known-to-be amethyst and it miss read it completely, so that was quite disappointing. Hard to trust the readings after that fail.