Fluorescence in lab diamonds?

[MMtwo]

I happened to be drawn into a discussion and another spot in the Internet. There seems to be consensus there that fluorescence is common in lab diamonds. How I understand it is that a blue fluorescence in a diamond is usually a hallmark of natural. Have I lost my mind?

 

[Old_Fossil]

I happened to be drawn into a discussion and another spot in the Internet. There seems to be consensus there that fluorescence is common in lab diamonds. How I understand it is that a blue fluorescence in a diamond is usually a hallmark of natural. Have I lost my mind?

This is an interesting topic for me as fluorescence is a phenomenon of physics. Fluorescence is a type of photoluminescence, which involves electronic transitions and energy emission at the atomic level. I look forward to the contributions of the experts here, but as I understand it, fluorescence is basically a glow (usually bluish) that some diamonds give off when you shine UV light on them—kind of like a blacklight effect. This happens because of tiny amounts of elements inside the diamond, most often nitrogen, that react to the UV light.

Like Brian Gavin, I embrace blue fluorescence as a positive differentiator, especially under UV light - but careful selection is key. I think his "Blue" collection offers fantastic value, as he hand selects the stones in that collection to avoid the milky or cloudy effects sometimes seen in weaker cuts or over-fluorescent stones. But I digress.

Most people think of fluorescence as something you only find in natural diamonds, and it is more common there. But lab-grown diamonds—whether they’re made using HPHT or CVD methods—can show fluorescence too. It just depends on how the diamond was grown and what trace elements ended up in it.

Natural diamonds usually glow with a more even blue color under UV, while lab-grown ones can have a wider range of fluorescence colors and might look a bit patchy or uneven when they glow. That’s mostly because of the different ways the two types of diamonds are formed.

Hope this helps, and I look forward to the others' contributions on this topic.

 

[Rockdiamond]

The only lab diamonds that exhibit fluorescence I’ve ever seen were CVDs that had been treated to turn pink. They’ve got orange fl.
I’ve never heard of colorless lab diamonds exhibiting fluorescence .

 

[DejaWiz]

According to Steven Rees, Executive Director, IGI North America Grading Laboratory:

We see fluorescence in about 10 percent or less of lab grown stones. The majority of those that have any are CVD (Carbon Vapor Deposition) grown, and tend to emit very slight yellow fluorescence. Only about one percent or less of HPHT (High Pressure High Temperature) produced stones emit fluorescence. When present it tends to be slightly orange.

source:

Diamond Fluorescence: The Bad and the Beautiful

Have you ever noticed a diamond that looks bright and glowing, or one dreary and dull? Both looks could be caused by fluorescence.

www.igi.org

 

[Rockdiamond]

Interesting…..
Has anyone seen an IGI report on a colorless lab diamond indicating fl??
10% sounds generous. If it is the case we’d see reports

 

[Texas Leaguer]

Blue fluourescence is common in natural diamonds - it is estimated that up to 30% of natural diamonds fluoresce and in the vast majority the color emitted is blue. This effect is generally associated with the trace element nitrogen. Most natural diamonds are characterized as type 1 based on a measurable presence of nitrogen.

Lab grown diamonds (in the normal color range) on the other hand are almost all type 2, with negligible amounts of nitrogen. Thus, they do not usually have the necessary chemistry to produce blue fluorescence.

Other colors of fluorescence and phosphorescence are sometimes seen in lab grown diamonds.

 

[MMtwo]

Thank you, Gentlemen. How puzzling that such a large group of folks argued that the fluorescence was common in lab diamonds. On clear diamonds, I had always believed a UV light was a rather reliable way to screen for natural diamonds, especially with a group of melee shining different levels of blue. The colored diamonds may fluoresce, but not the clear non-colored labs. Given the amount of diamonds you touch, your input is very appreciated.

 

[lovedogs]

Thank you, Gentlemen. How puzzling that such a large group of folks argued that the fluorescence was common in lab diamonds. On clear diamonds, I had always believed a UV light was a rather reliable way to screen for natural diamonds, especially with a group of melee shining different levels of blue. The colored diamonds may fluoresce, but not the clear non-colored labs. Given the amount of diamonds you touch, your input is very appreciated.

those folks are definitely wrong. Fluor is super rare in lab diamonds. I wonder why they thought that???

 

[freddyboston]

Interesting…..
Has anyone seen an IGI report on a colorless lab diamond indicating fl??
10% sounds generous. If it is the case we’d see reports

very rare but a few (faints and slights) do exist...
who knows what color it is or how uniform it is distributed across the stone...

 

[Karl_K]

What can be confusing is that UV reaction is used to sort mined from CVD from HPHT however they use different wavelengths of UV to do so.
This is not the report UV reaction or real world UV reaction. (365nm and 400nm)
Diamond fluorescence is measured in the lab at 365nm and in the real world on your finger the most visible reaction is likely going to be from 400nm UV.
The wavelengths to determine type are much shorter wavelengths and vary a bit from device to device but one example is 254nm.
The more reliable detectors use 3 wavelengths of UV light.

 

[Rockdiamond]

Awesome work guys!
@freddyboston
I should have realized I can check this myself.
I did a search for Lab D-Z stones- with no other parameters and got 1,210,838 results.
Add in all levels of fluorescence?
546 results.
Then, looking over the results, about half were actually pinks which were miscatagorized as D-Z
The 10% figure is a bit optimistic, to say the least......

 

[DejaWiz]

Interesting…..
Has anyone seen an IGI report on a colorless lab diamond indicating fl??
10% sounds generous. If it is the case we’d see reports

I agree that 10% sounds...a bit generously inflated.
The quote was from 2023, and no telling how old the quoted metrics were when the statement was made - could have been half a decade old data at that point, so improvements in grown crystal quality up to that point may not have been ratified data, yet.

 

[Texas Leaguer]

At this point, an enterprising grower might try to make lower colors (I-J-K) with with blue fluorescence. An interesting little niche for lab grown!

It may not be as simple as adding nitrogen to the growth environment though. The nitrogen needs to be incorporated into the carbon lattice in specific configurations. Not sure that can be tailored into either of the growth methods.

 

[Garry H (Cut Nut)]

Awesome work guys!
@freddyboston
I should have realized I can check this myself.
I did a search for Lab D-Z stones- with no other parameters and got 1,210,838 results.
Add in all levels of fluorescence?
546 results.
Then, looking over the results, about half were actually pinks which were miscatagorized as D-Z
The 10% figure is a bit optimistic, to say the least......

Excellent work David. I bet if you did that for D to say H there would be very few with fluoresnce.
Also what color?
White is most common in long wave I believe.

 

[oldminer]

The reporting of fluorescence truly should be connected to the wavelength of UV light being used. The Lab Reports all are using 365nm as the standard. You get more fluorescence from light closer to 400-430nm, but labs don't use that wavelength. The 365nm choice keeps reporting fluorescence less prevalent.

When testing for Lab Created diamonds I use 405, 365 and also 240nm wavelengths. The 240nm makes almost all Lab stones fluoresce and some to phosphoresce, but none of the formal reports we rely on tell any clients or users of these results even though they commonly use both 365 and a shorter wavelength such as 240nm. The results of using short wave UV are an excellent screening tool, but fluorescence to short wave UV has no effect on visual color grading because shortwave UV is thankfully not a component of our environment

 

[Garry H (Cut Nut)]

The reporting of fluorescence truly should be connected to the wavelength of UV light being used. The Lab Reports all are using 365nm as the standard. You get more fluorescence from light closer to 400-430nm, but labs don't use that wavelength. The 365nm choice keeps reporting fluorescence less prevalent.

When testing for Lab Created diamonds I use 405, 365 and also 240nm wavelengths. The 240nm makes almost all Lab stones fluoresce and some to phosphoresce, but none of the formal reports we rely on tell any clients or users of these results even though they commonly use both 365 and a shorter wavelength such as 240nm. The results of using short wave UV are an excellent screening tool, but fluorescence to short wave UV has no effect on visual color grading because shortwave UV is thankfully not a component of our environment

In patent applications for automated Fluorescence grading the GIA mention both 365 and 385nm, both invisible. I believe the GIA may well be using 385nm (which generates a stronger N3 blue fluoro than 365nm).
More than half of diamond fluoresce in that longer wavelength.

 

[oldminer]

The GIA choosing to change to 385nm would go against their obvious previous bias to minimize UV fluorescence when it was considered negative by the trade. Now that blue UV fluorescence has taken on a niche following and acceptance, chasing that trend is more in line with consumer and trade demand for some way to know their diamond is Mined, differentiating Mined from most of the colorless Lab material which is not generally reactive to LWUV or 400nm+ blue light.

Does anyone have the historical reason 365nm has been the standard LWUV lighting for diamond fluorescence grading since the 1950's? Was this the only commercially available wavelength tube or bulb available at the time? Is this change because of the LED and laser revolutions resulting in large selections of wavelengths?

 

[Texas Leaguer]

The GIA choosing to change to 385nm would go against their obvious previous bias to minimize UV fluorescence when it was considered negative by the trade. Now that blue UV fluorescence has taken on a niche following and acceptance, chasing that trend is more in line with consumer and trade demand for some way to know their diamond is Mined, differentiating Mined from most of the colorless Lab material which is not generally reactive to LWUV or 400nm+ blue light.

Does anyone have the historical reason 365nm has been the standard LWUV lighting for diamond fluorescence grading since the 1950's? Was this the only commercially available wavelength tube or bulb available at the time? Is this change because of the LED and laser revolutions resulting in large selections of wavelengths?

I do believe the historical choice of 365 was based on practicality/availability. Seems like I remember reading that in background of one of the GIA studies. We have to remember that the main reason fluorescence was even reported on initially was just to have another data point for identification. So, as long as the equipment and observations were consistent, any chosen wavelength would achieve the purpose.

Today fluorescence is much more involved from a market perspective, having not only a role in ID, but also a bearing on performance and valuations. Thus, I think it makes sense to expand the testing parameters.

 

[Karl_K]

Does anyone have the historical reason 365nm has been the standard LWUV lighting for diamond fluorescence grading since the 1950's? Was this the only commercially available wavelength tube or bulb available at the time? Is this change because of the LED and laser revolutions resulting in large selections of wavelengths?

Yes, the available at reasonable cost bulb was advertised as 365nm.
It was a mercury based UV light tube which has a native emission peak at around 365nm.
It was adopted for a lot of things as a result.

LEDs are available binned in a lot of different UV wavelengths.
At the consumer level there is a lot of fraud selling ~400nm LEDs as more expensive wavelengths.
However on the commercial side you can get properly binned LEDs.

 

[lovedogs]

Its been so hard to find an overblue natiral diamond. I would jump for joy if someone made labs with intense fluor.

 

[Garry H (Cut Nut)]

It was a mercury based UV light tube which has a native emission peak at around 365nm.
It was adopted for a lot of things as a result.

LEDs are available binned in a lot of different UV wavelengths.
At the consumer level there is a lot of fraud selling ~400nm LEDs as more expensive wavelengths.
However on the commercial side you can get properly binned LEDs.

Karl is correct, the mercury tube.
First introduced to enable identification of various gemstones and treatments.
Was sitting in the lab so was used to report fluorescence.
The GIA, i believe, always reported on fluoro as an ID factor. Remember from ever that blue fluorescent diamonds cost more, until the FluoroGate event in Korea in 1993.
In 1993: the GIA updated the terminology to the current 5-grade scale:

 

[Garry H (Cut Nut)]

The main reason that the Mercury vapor lamp works for diamonds is that the radiation extends to the visible violet.
However that source also lights up a lot of LGD (as opposed to 385 or even better still intense 405nm).
This chart I clipped at 550nm.
400-550nm is the human visible range: