Gemindicator, relyable?

Any body knows about Gemindicators, are they relyable?
Kneed all information that i can get.
Thank you
Regards Fredrik

Hi Fredrik.

I had the oppurtunity to test a gemindicator from Presidium and i can say from my experience that it was not reliable. I tested a well known gemstone and it gave different answer 2 of 4 times. The same to the Diamond/Moissanite tester. I tested 2 indian made moissanites and they passed for diamonds.
My opinon of the electronical devices is that they are not reliable. You have to work with the traditional equipment.

Pierre Gunnarsson


I Thank you very much for your opinion. I value every aspekt of it.

I have used the Presidum Gem Tester for years as a “First” test for gemstone type and found it to be a very reliable tool. When my first test wand got to be about 7 years old, however, I started to get “funky” readings based on the position of the wire connecting the probe to the device. I purchased a replacement wand am now back up to acceptable results with consistent readings. While I mostly use my Presidum for colored stones, I have found many supposed “diamonds” to be simulants, and found many, many simulants sold as the real deal. real chrome diopside and tanzanite always read in a narrow zone. Too many uninformed sellers out there attempting to sell sky-blue topaz as Aquamarine. It will also show a glass filled Madagascar Ruby as glass or corundum depending where the point is placed on the gem. Lab-created Sapphire, Ruby, Spinel, Topaz, and colored quartz are frequently sold as the real-deal out of Thailand, China, India and even the USA. Usually, the Presidum will reveal the type of gem you test, so if you are looking at a reported Sapphire and the tester reads Topaz, that tells you something is funky. Often I find synthetic or simulant stones where EITHER the Thermal Conductivity (the parameter measured by the Presidum) reading is out of spec or the RI is out of spec. The real key is to test several different areas on cut or rough stone, then combine the initial results with other tests such as the refractometer, filters, and 90 power magnifier. As an initial test, I feel the Presidum Gem Tester is a Very Reliable first test for a gemstone. Now, don’t go buying Tektite Moldovite or Helenite gems and expect any reading other than what they are-GLASS.


HI, what is the model of Presidum you use for gem testing? And any idea which is the best / most reliable gem tester of even the more rare gem subtypes (garnets, tourmalines, spinel)

This is the model refering above,
They could test garnets, tourmalines, spinel etc…
But I wouldn’t use it to conclude the identity of the gem, but it’s great as a quick first test.
Hope it helps.

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