

💎 Identify gems like a pro—fast, precise, and effortlessly sleek.
The Presidium Instruments Gem Indicator (PGI) is a handheld, ergonomic tester designed specifically for identifying diamonds and 31 common colored gemstones. Featuring the industry's thinnest retractable thermoelectric probe tip, it delivers quick, reliable results in under 6 seconds displayed on a clear LED screen. Its advanced color input function enhances gemstone differentiation, making it an essential tool for jewelers and gemologists seeking precision and portability.






| ASIN | B06X979666 |
| Best Sellers Rank | #199,088 in Arts, Crafts & Sewing ( See Top 100 in Arts, Crafts & Sewing ) #83 in Jewelry Diamond Testers |
| Customer Reviews | 3.8 3.8 out of 5 stars (55) |
| Date First Available | June 3, 2016 |
| Is Discontinued By Manufacturer | No |
| Item Weight | 11.2 ounces |
| Item model number | PGI |
| Manufacturer | PRESIDIUM |
| Package Dimensions | 8.1 x 3.4 x 2.4 inches |
L**.
Testing gemstones
Excellent Seller! Purchase a Presidium gemstone tester! I love it! Thank you!
B**A
Inaccurate - worked for less than a year before it became unusable
It worked for less than a year. For the price point, it should be way better quality. It now reads “slip detected” constantly - even when it’s not against the stone yet. It’ll provide a reading before the tip has touched the stone. You can test the same stone twice to multiple different results. Save your money & buy any other machine to help you out.
A**A
A good Useful Tool to have
Great tester, as other reviews have stated You have to have some Knowledge of Gemstones while using this pen which I had no problem with, you can go on the Presidium Website and Download the Spreadsheet of Gems if you’re not sure. As far as Diamond if I wasn’t holding the pen straight and at an angle it would read Sapphire and Ruby, you need to hold the Tester at a straight angle to get an accurate reading, held straight tested for only Diamond. I just wish this one Included an option for testing moissanite!
J**N
Not what I expected for the price
I found this gem tester to be very inaccurate in that it gives you a wide range of possible stones. It also has a very difficult time with blue and green stones calling them glass most of the time. For the $300 plus price I expected it to be more accurate and informative. I have an RI tester that is so much better but is hard to use on smaller stones. That was my main reason for the purchase of the new tester with a small tip. It will press against small gems but the readings are not very accurate.
R**K
Take the bad reviews with a grain of salt.
I found that when using this product, it works every single time, every gemstone that I used it on came back with the exact right name. Some people have been giving bad reviews about this product. I feel that they weren’t using it right, or didn’t read the instructions all the way that you have to download, or they need a new tip.
G**E
Amazing product don’t worry about reviews
I was worried because of some of the other reviews but I got this product and it is an excellent diamond tester. It can also test some of my Amythyst and even showed me that a few family heirlooms were glass hahaha. It doesn’t say Cubic Zicornia but it will give you the same 8 options so you know what it means. And most importantly, if you test CZ, diamond will not be one of those options! I’m happy with it. Definitely recommend. It can test rubies and sapphires too.
M**A
A real waste of money
I should follow previous reviews, is a total deception. I have an antique ring and I wasn’t sure about gems, could be spinnel or ruby, and selecting red color the possible gems are spinnel and ruby!! It must be calibrated everytime you switch gems, that’s not as important as the fact that alternatives for a same gem doesn’t solve the issue of knowing which gem is in front of you. I think previous version, the one not portable, must be a better choice, cause there’s no way to get so many options.
C**O
Not accurate
Challenging to figure out… Did not seem accurate
A**O
Falto el instructivo y caja vino dañada tratare de bajar el manual de internet , medio difícil de utilizar
S**N
Keep the operating procedure simple to follow/understand. Can you share a detailed and simple procedure to start using including how to test different colored gemstones?
Trustpilot
2 days ago
2 weeks ago