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diamond testing
- Thread starter mike k.
- Start date
bootyhoundpa
Well-known member
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..
Flintstone
Well-known member
GOOD GLASS???
WaterWalker
Well-known member
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.
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.
Champ Ferguson
New member
WaterWalker said:
^^^^^^^^ correct answer. Tho I think you meant to say Index of Refraction or specific gravity instead of reflectivity .
edited for spaillin.
WaterWalker
Well-known member
Thanks, Any day I do not learn something is a wasted day. You made my day today!
GeorgeinSC
Well-known member
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.
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.
Fishers Ghost
New member
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
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
Champ Ferguson
New member
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.
WaterWalker
Well-known member
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
Thermal - heat transfer
Resistivity - electrical transfer
Refraction - light transfer
Hardness - resistance to marring form other materials
WaterWalker
Well-known member
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 - (10[sup]11[/sup] to 10[sup]18[/sup] 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
Specific gravity - is 3.5 to 3.53
Thermal conductivity is measured in W/(m·K)
Electrical resistivity is measured in GΩ·m - (10[sup]11[/sup] to 10[sup]18[/sup] 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
Fishers Ghost
New member
Champ Ferguson said:
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
Champ Ferguson
New member
GIA? 
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.
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.
Fishers Ghost
New member
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.
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.
Champ Ferguson
New member
So not GIA...?
Fishers Ghost
New member
No not GIA. Was FGAA .
Sorry if I am not to GIA standards.
Sorry if I am not to GIA standards.
OldBeechnut
Well-known member
I have the old cheapo diamond tester, diamond selector II. Can't say I find enough bigger diamond rings to say I need anything better. And if I do finding something worthy I'll run it up to the local jeweler. They are always willing to help for free.
Champ Ferguson
New member
Fishers Ghost said:No not GIA. Was FGAA .
Sorry if I am not to GIA standards.
Sorry, didn't mean to insult + not trying to call you out. Your self description and claims hinted at GIA and I wanted to understand your quals so I could tailor my post better..
GeorgeinSC
Well-known member
A few years back I found a beautiful 14k marked ring with a beautiful main stone and smaller stones on the split shank. Had to wait for daylight to see the hallmark. Tested it with my cheap tester and it claimed it was diamonds. I was elated to have found my first diamond ring. Main stone appeared to be about a fuyll carat.
Took it to a local jewelry shop and the young lady looked at it carefully with her loupe then tested it and proclaimed that it was a diamond. She said it appeared to be a high quality diamond.
Happened to be in a jewelry shop in another state getting the battery in my watch, that i found at the beach, replaced. Young lady said that is an expensive watch and i told her no it was cheap as i found it detecting. She said her husband detected but never found anything but rusty junk.
Later i had to have the band fixed so i took a couple of my finds along to show her. The Jeweler was in and he wanted to look at my "diamond" ring. He studied it very carefully, tested it for diamond, studied it some more and then tested it for mossionite. It tested positive for mossionite.
Later i took it to another GIA certified gemologist and she after much examination and testing said it is a mossionite.
Took it to a local jewelry shop and the young lady looked at it carefully with her loupe then tested it and proclaimed that it was a diamond. She said it appeared to be a high quality diamond.
Happened to be in a jewelry shop in another state getting the battery in my watch, that i found at the beach, replaced. Young lady said that is an expensive watch and i told her no it was cheap as i found it detecting. She said her husband detected but never found anything but rusty junk.
Later i had to have the band fixed so i took a couple of my finds along to show her. The Jeweler was in and he wanted to look at my "diamond" ring. He studied it very carefully, tested it for diamond, studied it some more and then tested it for mossionite. It tested positive for mossionite.
Later i took it to another GIA certified gemologist and she after much examination and testing said it is a mossionite.
Fishers Ghost
New member
Champ Ferguson said:No not GIA. Was FGAA .
Sorry if I am not to GIA standards.
Sorry, didn't mean to insult + not trying to call you out. Your self description and claims hinted at GIA and I wanted to understand your quals so I could tailor my post better..
No problems. All is good.
being a Gemmo has been interesting.
I recall the first gem Show I went to and set up a gem testing stall along with 4 other Gemmologists.
We asked people to bring their family heirlooms along for testing.
On the first day, Out of 48 very nice looking gold and gem-set antique items only one was the real deal. By the end of the day I was becoming depressed from seeing the looks of disappointment .