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.
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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
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Also topaz register’s very highly on a diamond tester…
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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
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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.
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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.
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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
I recently invested in a new identification tool that I am really enjoying. It’s really two tools that connect wirelessly. The Gemlogis Mantis conducts a thermal test on all polished gemstones and sends the result to the Gemlogis Bleu which will display all the possible matches for the reading. Then you choose the color of the stone and it will narrow down the list to one or more matches. Just like the Presidium testers, it will not be conclusive in all cases, but will tell you what it definitely is not. Using a refractometer, UV light or testing specific gravity will usually pinpoint the answer.
Also, when testing a diamond the Mantis will use an ultraviolet test. I’ve not found it to be wrong about a diamond yet.
Has any other IGS member used this tool?
I purchased it two months ago on eBay for $409. Free shipping
Rub them real hard on corundum emery cloth or Silicon Carbide emery cloth and find out !! If they are diamonds, then they will eat the emery cloth abrasive … if they are not, then the emery cloth abrasive will eat the stone. ;)) You can get the emery cloth at Harbor Freight Tools.
You can take them a mainstream jewelry store and they’re likely to have a higher-quality diamond tester (for store merchandise security purposes) if they sell diamonds, as diamonds are often supposed to be tested every time they leave and return to a case. I work at Kay Jewelers and we have three in our tiny little store alone. Only thing that has ever tested false-positive on them is very high-quality white moissanite (your typical moissanite/topaz/white sapphire/CZ/glass won’t register as diamonds on them) which was identified by the maker’s mark on the girdle. It was def a high-quality synthetic. The guy tried really hard to pass it off as a $40,000 3 ct diamond.
But, as they said above, you get what you pay for. If you want a really reliable tester, it’s going to be much more expensive. I’d just see if I could find a local jewelry store that’ll let you “borrow” theirs for a couple minutes for free unless you think you have a use for one in the long term and it’s worth making a rather large investment.
Buy a Presidium tester. They’re pretty darn good.