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diamond testing
Posted by: mike k.
Date: January 10, 2019 02:58PM
Ok ,I tried my diamond tester on a few rings and I know that when it climbs up to red and flashes -its a diamond . Other times , if its glass ,it doesnt move much . But what is it if it stops just before the diamond alert ?? - thanks

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Re: diamond testing
Posted by: bootyhoundpa
Date: January 10, 2019 04:55PM
Ive only ever owned one tester and it recently died but i do recall that something called moissanite can come close to mimicking diamond readings..

Re: diamond testing
Posted by: Flintstone
Date: January 10, 2019 05:58PM
GOOD GLASS???

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Re: diamond testing
Posted by: WaterWalker
Date: January 10, 2019 07:14PM
Depending on the tester, battery, temperature, cleanliness of the stone's surface and initial setting you will see slightly different results.

Older testers will evaluate moissanite and diamonds as the same, no questions asked.

Newer testers will first test the thermal conductivity to determine if a stone is moissanite / diamond OR not. Then the tester will test the moissanite / diamond resistivity to differentiate between the two.

No electronic tester that I have used will tell if the stone is glass (junk) or a semiprecious stone such as white topaz. When you get that specific reflectivity is the way to test the stone. Don't discard the stone just because a tester shows it is not a diamond. Also don't be fooled with black, brown, green and other colored stones as they just may be a diamond! - even if they are set in silver.

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Re: diamond testing
Posted by: Champ Ferguson
Date: January 11, 2019 12:16PM
Quote
WaterWalker
Depending on the tester, battery, temperature, cleanliness of the stone's surface and initial setting you will see slightly different results.

Older testers will evaluate moissanite and diamonds as the same, no questions asked.

Newer testers will first test the thermal conductivity to determine if a stone is moissanite / diamond OR not. Then the tester will test the moissanite / diamond resistivity to differentiate between the two.

No electronic tester that I have used will tell if the stone is glass (junk) or a semiprecious stone such as white topaz. When you get that specific reflectivity is the way to test the stone. Don't discard the stone just because a tester shows it is not a diamond. Also don't be fooled with black, brown, green and other colored stones as they just may be a diamond! - even if they are set in silver.

^^^^^^^^ correct answer. Tho I think you meant to say Index of Refraction or specific gravity instead of reflectivity .


edited for spaillin.





Banned this clown for calling Windy City a crook in detector sales and from pm he sent me.



Edited 2 time(s). Last edit at 01/11/2019 12:17PM by Champ Ferguson.

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Re: diamond testing
Posted by: WaterWalker
Date: January 11, 2019 02:37PM
Thanks, Any day I do not learn something is a wasted day. You made my day today!

Re: diamond testing
Posted by: GeorgeinSC
Date: January 11, 2019 06:48PM
A few years back I found a "Diamond Rin g" at the beach. Brought it home and tested it with my diamond tester. It screamed diamond. I took it to a local jewelry store and the young lady studied it carefully, tested it with their professional diamond tester and said that it was a real diamond and of very high quality.

I was later in a jewelry shop in another state to get the battery in my watch battery changed and in talking to one of the ladies who worked there the subject of detecting came up. Her husband detects. I later had to go back to the shop to get the band on my watch repaired and took some of my finds to show her.

The Gemologist asked if he could look at my "Diamond Ring". He kept studying it with his loupe and then used his diamond tester. He said I don't think that it is a diamond as I am seeing too much color and light transmission. He then used his tester for moissanite and it tested positive.

So my fortune from that ring disappeared. He did say that his cost on a 14k Moissanite ring like mine would be between 5 and 6 hundred dollars.

So diamond testers that are not testing for Moissanite will say that it is a diamond.



Minelab Sovereign GT With an assortment of coils
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Re: diamond testing
Posted by: Fishers Ghost
Date: February 02, 2019 03:29PM
All of the reflectivity meters are very hit and miss gem testers. At best they will get you into the ball park and then you need to do further testing to verify the stones ID.
A 10 X loupe and some diamond ID training is all you need. Refractometers do not help much for diamond ID because they cannot read the high refractive index of diamond.

if your reflectivity tester is showing borderline between diamond and some lower reading then it is possible that your tester is not calibrated correctly for the size stone you are testing, the probe tip is dirty,these testers are often temperature sensitive, tester battery could be getting a bit low, your stone may be a sapphire. Moissanite tests as diamond on the reflectivity meters.The Moissanite reflectivity meters can often give erroneous results. Moissanite is double refractive diamond is single refractive.
Do not rely on those cheap made in China reflectivity meters to give a positive ID on all diamonds, at best they can suggest that the stone may be a diamond but they cannot give a diagnostic ID.

fishers ghost
EX FGAA

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Re: diamond testing
Posted by: Champ Ferguson
Date: February 03, 2019 08:23AM
If your instrument cant measure the Index of Refraction of a diamond, you don't have a very good one. Also, there are refractivity oils that you can use for this.





Banned this clown for calling Windy City a crook in detector sales and from pm he sent me.

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Re: diamond testing
Posted by: WaterWalker
Date: February 03, 2019 08:51AM
There are four tests that I know of for testing diamonds:

Thermal - heat transfer
Resistivity - electrical transfer
Refraction - light transfer
Hardness - resistance to marring form other materials

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Re: diamond testing
Posted by: WaterWalker
Date: February 04, 2019 04:59AM
Getting a bit more technical about diamond characteristics, let me add two more testing of diamonds that I forgot to add in yesterday's posting.

Specific gravity - is 3.5 to 3.53
Thermal conductivity is measured in W/(m·K)
Electrical resistivity is measured in GΩ·m - (1011 to 1018 Ω·m). NOTE: resistivity is the inverse of conductivity
Refractive index of diamond (as measured via sodium light, 589.3 nm) is 2.417
Optical absorption is measured with a spectrophotometer that analyze the infrared, visible, and ultraviolet absorption and luminescence spectra
Hardness is measured in Mohs -10

Re: diamond testing
Posted by: Fishers Ghost
Date: February 21, 2019 04:23AM
Quote
Champ Ferguson
If your instrument cant measure the Index of Refraction of a diamond, you don't have a very good one. Also, there are refractivity oils that you can use for this.

My refractometer reads to RI 1.81 It is a true refractometer. It is good enough for my needs and has been for the past 30 years.
There are other instruments that are referred to as refractometers such as the Presidium II and the digital red out is supposed to be refractive index but the instrument is actually a reflectometer and the readings are a measure of the reflectivity of the polished surface of the stone/gem being tested and are not refractive index.

The heat transfer instruments are good for ball park readings only and are not in any way a diagnostic tester.

I know how to ID diamond with a hand lens only as I am a gemmologist

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Re: diamond testing
Posted by: Champ Ferguson
Date: February 21, 2019 10:48AM
GIA? :wink:

eta: totally agree the heat instruments are ballpark only.
also, claiming to positively ID diamonds with only a handlens is folly. if you are certified, you know that.





Banned this clown for calling Windy City a crook in detector sales and from pm he sent me.



Edited 1 time(s). Last edit at 02/21/2019 10:50AM by Champ Ferguson.

Re: diamond testing
Posted by: Fishers Ghost
Date: February 21, 2019 05:32PM
I will agree that an inexperienced gemmo might not be able to ID a diamond with a 10x hand lens only and also that a flawless perfectly cut and polished stone would require further testing.
All I can say is that in 30 years of gem testing and to the best of my knowledge I have not miss identified a diamond yet using a hand lens. I will however verify my loupe test by whatever means are necessary on occasion when doubt enters my mind. For eg on rare occasions I have had to resort to spectroscopic testing and sg tests. I have even sent one item off for mass spectrometer testing.
I am retired from gem testing now but still dabble a bit and still try to keep up with all of the man made stones on the market today. Some are becoming tricky to separate from the genuine article.

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Re: diamond testing
Posted by: Champ Ferguson
Date: February 22, 2019 12:41PM
So not GIA...?





Banned this clown for calling Windy City a crook in detector sales and from pm he sent me.

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