I bought a Diamond Selector 2 and was testing a few different stones that I picked up. The diamond tester showed that they were diamonds. Can the diamond tester show a false positive? If so what other kind of stones will set it off?
Hello … this instrument is a Thermal Conductivity Tester. It basically indicates how fast heat is moving out of the tip of the device into and through your material under test. This type of $15, manufactured in China, sold on ebay device gives false “diamond” indications all the time. You should set it or calibrate it to a KNOWN diamond. That will help some; however, you get what you pay for. Invest in a Presidium unit for more accurate results. Any material that has crystalline structure will pass heat and give you a possible false positive with this unit. Materials with no crystalline structure such as glass are insulators and will give no indication of heat transfer. Cubic Zirconia is an insulator and will not pass heat as well. Moissanite does pass heat and will give you a false positive on this unit most of the time. These instruments are not proving if the material is a diamond or not; they are indicating if the material is passing heat like a diamond should. Pure silver will pass heat at the rate that a diamond does, but that doesn’t make the silver a diamond! :))) None of your stones in the photo appear to be rough diamond to me. All the best in your gemological endeavors.
I came across the same issue with some stones that I thought were diamonds but they turned out to be topaz as much as I wish that they were diamonds they were topaz see topaz has a crystal structure that is quite similar to Diamond they have a similar specific gravity the best way to tell is to check the refractive index topaz being 1.6 fish don’t quote me on that and Diamond being 2.7
Also topaz register’s very highly on a diamond tester…
How do you check the refractive index? And thank you for the update
the second one from the right and the one below it are ruby I would guess. and ruby(aka corundum) registers very high on that tester, if you can get a known diamond like from a ring or something, and test it with your tester. A real diamond should make your tester shoot up very quickly, now try the stones and see if they shoot up as quickly on the scale. sometimes ruby and topaz will go as high as a diamond on the scale, but not as quickly as a diamond
I have tested a real diamond and it went up in the red in a flash. The second on the left on the top shoots up pretty fast but not like a diamond
You need a .refracometer at minimum you need a 10x corrected loupe,and other gemological equipment.A course in Gemology is a must also.
The answer to the question of can it give a false positive… yes! I have had them test as diamond on Corrundum, topaz, sunstone etc. I may suggest a presidium thermal tester, they are far more accurate.
Strongly agree! See my post above.
Wonder where i can find one of them thermal testers? And the cost would probally give me a heart attack. But i surevso thank all yall for the info. Im off to carve another stone