Article Over Grading of Blue Fluorescent Diamonds Revisited

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

With an advanced degree in electronic communications, you might think that I would be more skilled in communicating diamond grading and other gemological concepts to the consumer. But that form of communication is a very different skill, that of a writer and journalist.

Graduate Gemologist Richard Wise is an expert in this form of communication, and he has applied his writing skills to the field of gems and the gem trade in his newly published book "Secrets of the Gem Trade, Second Edition”.

His unique skills in journalism combined with extensive academic and real world knowledge and experience in gems and jewelry have resulted in an outstanding very readable work for the consumer public. “Secrets” reads like a novel as it communicates to the gem and jewelry lover sometimes technical and scientific information along with the secrets, romance and beauty of the diverse and wonderful world of gems. The gorgeous imagery throughout this work is icing on a delicious book of gems that encompasses essential aspects of the whole gem trade, from mine to jeweler.

I post this review here in hopes that those following this thread on blue fluorescent diamonds will take advantage of and enhance their knowledge and understanding of this subject from his perspective in the three chapters “Blue-white Diamonds”, “Colorless Diamonds”, and “Golconda or Type IIa Diamonds”.

Here are a couple of relevant excerpts that are fleshed out in these chapters.

“Historically, highly transparent diamonds with white and bluish white body color were considered gems of the finest water, a rare quality known as river. In the late 19th century, fully one hundred years after the Indian mines were tapped out, diamonds from southern Africa began to flood the market. Some of these were blue fluorescent diamonds. According to the legendary gemologist, Frank Wade, writing in 1915, those that did not bleed color, that is, did not appear yellowish face up in the low ultraviolet of incandescent light were added to the river category.”

“What does this mean for the connoisseur? River quality stones are very rare, but these original blue white type IIa’s and blue fluorescent diamonds that hold their color (in low UV light) are well worth the seeking and likely to be priced well below their true value.”

Check out: www.secretsofthegemtrade.com..... The Introduction and Overview to Blue White Diamonds is one of the sample chapters on the website. ( http://secretsofthegemtrade.com/?page_id=32 )

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

With an advanced degree in electronic communications, you might think that I would be more skilled in communicating diamond grading and other gemological concepts to the consumer. But that form of communication is a very different skill, that of a writer and journalist.

Graduate Gemologist Richard Wise is an expert in this form of communication, and he has applied his writing skills to the field of gems and the gem trade in his newly published book "Secrets of the Gem Trade, Second Edition”.

His unique skills in journalism combined with extensive academic and real world knowledge and experience in gems and jewelry have resulted in an outstanding very readable work for the consumer public. “Secrets” reads like a novel as it communicates to the gem and jewelry lover sometimes technical and scientific information along with the secrets, romance and beauty of the diverse and wonderful world of gems. The gorgeous imagery throughout this work is icing on a delicious book of gems that encompasses essential aspects of the whole gem trade, from mine to jeweler.

I post this review here in hopes that those following this thread on blue fluorescent diamonds will take advantage of and enhance their knowledge and understanding of this subject from his perspective in the three chapters “Blue-white Diamonds”, “Colorless Diamonds”, and “Golconda or Type IIa Diamonds”.

Here are a couple of relevant excerpts that are fleshed out in these chapters.

“Historically, highly transparent diamonds with white and bluish white body color were considered gems of the finest water, a rare quality known as river. In the late 19th century, fully one hundred years after the Indian mines were tapped out, diamonds from southern Africa began to flood the market. Some of these were blue fluorescent diamonds. According to the legendary gemologist, Frank Wade, writing in 1915, those that did not bleed color, that is, did not appear yellowish face up in the low ultraviolet of incandescent light were added to the river category.”

“What does this mean for the connoisseur? River quality stones are very rare, but these original blue white type IIa’s and blue fluorescent diamonds that hold their color (in low UV light) are well worth the seeking and likely to be priced well below their true value.”

Check out: www.secretsofthegemtrade.com....... The Introduction and Overview to Blue White Diamonds is one of the sample chapters on the website. ( http://secretsofthegemtrade.com/?page_id=32 )

I can't comment on the Secrets as I have not read that yet. But I recently read Richard Wise's book The French Blue about the journeys of John Baptiste Tavernier in the 17th centrury and ultimately his purchase of the diamond that would become the most famous in history. Absolutely brilliant historical novel. A fascinating read for anyone who loves gems! Wise is an experienced jeweler, knowledgeable gemologist and gem trader, and an excellent writer.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Have not stopped thinking and reading about this topic.

A few updates.
It seems GIA have been using more accurate and narrow banded LED UV sources for a long time in their lab - first patents were granted in 2004 for digital grading systems. I wish they were more forthcoming with GTL processes.
The most recent application is for an adaption and new instrument for fancy shapes. Just as fancy shaped diamonds generally increase the amount of color we see in the same material used for round cuts - so too does the intensity of fluorescence in fancy shapes appear more apparent.
http://patft.uspto.gov/netacgi/nph-...d=PTXT&s1=7,102,742&OS=7,102,742&RS=7,102,742 Note they have crept a little higher to 370nm in the LED light source. Wish they would go higher to 400nm.


http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects states that there is twice as much blue created by just visible light slash Ultra Violet light (400nm) than at the Long Wave UV standard that is used simply because that Mercury vapour tube lights were once apon a time (in a far away land) the only source of UV light.
Quote " For example, the intensity of N3 luminescence (measured at 439 nm) when excited by 400 nm excitation is approximately double that of the same emission measured at 360 nm excitation (figure 6)."
This is also evident in the Thomas Hainschwang, Gemlab chart MC used in his article. A point I have made before that was ignored is that ordinary visible light produces a strong N3 blue fluorescence too. The range of the Solarmeter that MC used does not go to the near visible spectrum. Also note that there are no window materials that block the wavelengths we really now should be discussing.

Unless I am mistaken GIA has not disclosed they have a digital fluorescence grading system, and given they have digital color grading patents, I do not think we know how GIA color grades diamonds. Since Michael never provided a full disclosure of the dates and grading reports on the stones he used in his study, I have no confidence that the "Over Grading" problem is a problem.

It may well be that Strong Blue fluorescent diamonds are now under graded by GIA for most lighting environments where there is adequate illumination to make small color grading distinctions possible.

Hi Michael,
Glad you are still alive and posting here.
Richard is a great story teller. I have the Blue book also.
Would you care to discuss my month old post with recent learnings?

 

[Sagebrush]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Brian,

Many thanks for the kind words about The French Blue. Like most writers, I write to be read and it is always gratifying to I hear from a reader who really enjoyed my work.

In the 2nd edition of Secrets Of The Gem Trade, I tried to go beyond the positions that I held in 2003, i.e. that the best dimensions for brilliance did not overlap those that delivered the best dispersion. I found Michael's analysis of cut/dispersion/brilliance a great aid. As I state in the book I had the opportunity of examining a diamond cut as Michael recommends. It was an exceptionally beautiful stone, more beautiful than any brilliant I have seen before or since.

I found his discussion of overgrading of blue fluorescent diamonds similarly useful particularly when coupled statements made by gemologists such as Shipley and Wade particularly when put together with my experience examining the aesthetic qualities inherent in Type IIa "Golconda" diamonds. It seems to me that Michael points are, like the best science, mostly self evident and easily verified experimentally.

Organizations such as GIA have made and continue to make important contributions to gemology. Most of us would not be where we are without the Institute's efforts over time. However, as organizations mature they become conservative and intolerant and less and less able to acknowledge and admit even the most obvious errors. This is the sort of institutional hubris that must be continually challenged if the science and human knowledge is to continue to grow. I believe we need people like Michael Cowing, men and women with the intestinal fortitude to challenge the received opinions of even the most sacred institutions. They are the mavericks, the ones who keep us honest.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Did I mention he is a good writer

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I've got to share this. Slightly off topic but in the category or "fluoro can be really cool".

We inspect all incoming diamonds for fluorescence as part of our overall gemological inspection process. This part of our evaluation is done in our photography darkroom where our light performance imaging is conducted.

This week an interesting diamond came through and Tim shot some images of it, as he does from time to time when cool stuff comes through. This stone has both blue and orange fluorescence, very localized.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I've got to share this. Slightly off topic but in the category or "fluoro can be really cool".

We inspect all incoming diamonds for fluorescence as part of our overall gemological inspection process. This part of our evaluation is done in our photography darkroom where our light performance imaging is conducted.

This week an interesting diamond came through and Tim shot some images of it, as he does from time to time when cool stuff comes through. This stone has both blue and orange fluorescence, very localized.

Most probably a diamond in diamond inclusion Bryan. But could also be another mineral.
Protogenetic, i.e. formed before the mineral that it is now included inside. They can be very hard to see and hence may not lower the clarity grade very much - a bit like twinning, but twins result from pressure / temp changes during crystal growth.


What is the stones clarity? Was there an inclusion in that area?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I've got to share this. Slightly off topic but in the category or "fluoro can be really cool".

We inspect all incoming diamonds for fluorescence as part of our overall gemological inspection process. This part of our evaluation is done in our photography darkroom where our light performance imaging is conducted.

This week an interesting diamond came through and Tim shot some images of it, as he does from time to time when cool stuff comes through. This stone has both blue and orange fluorescence, very localized.

Most probably a diamond in diamond inclusion Bryan. But could also be another mineral.
Protogenetic, i.e. formed before the mineral that it is now included inside. They can be very hard to see and hence may not lower the clarity grade very much - a bit like twinning, but twins result from pressure / temp changes during crystal growth.


What is the stones clarity? Was there an inclusion in that area?

Hey Garry,
It's an E VVS2, so not much at all visible in the way of inclusions.

 

[Tekate]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Wow that truly fascinating. And helpful. thank you.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I've got to share this. Slightly off topic but in the category or "fluoro can be really cool".

We inspect all incoming diamonds for fluorescence as part of our overall gemological inspection process. This part of our evaluation is done in our photography darkroom where our light performance imaging is conducted.

This week an interesting diamond came through and Tim shot some images of it, as he does from time to time when cool stuff comes through. This stone has both blue and orange fluorescence, very localized.

I am late seeing this but that is really awesome. Thanks for sharing.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I've got to share this. Slightly off topic but in the category or "fluoro can be really cool".

We inspect all incoming diamonds for fluorescence as part of our overall gemological inspection process. This part of our evaluation is done in our photography darkroom where our light performance imaging is conducted.

This week an interesting diamond came through and Tim shot some images of it, as he does from time to time when cool stuff comes through. This stone has both blue and orange fluorescence, very localized.

I am late seeing this but that is really awesome. Thanks for sharing.

It would definitely be a diamond in diamond inclusion Bryan. They can be impossible to see and would probably be labelled as twinning (which is not mineralogically accurate). This type of inclusion is called xenolithic - the term means foreign inclusion that pre-existed before the formation of the rock or mineral that it is included in. Eclogitic = formed at the same time, and that is not likely the case for this inclusion.

PS it would be nice if Michael would answer some of the questions he avoids. It is very clear to me that GIA and everyone are using the wrong frequency UV longwave light. The correct frequency is the 390 to 400nm range which is abundant and in the near visible range. It is not blocked out by window glass -not even by specialist UV films etc. I guess his not answering = he realizes it is game set and match.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Calling everyone back to this topic.
GIA use around 366nm long wave UV because it was the only practical standard (based on mercury vapour) and it was useful because the long and short waves enabled some great gem identification. But totally meaningless for diamond identification.
The article by Yun Luo and Christopher Breeding Gems & Gemology 2013 file:///D:/Dropbox/Dropbox/My Documents1/Book/SU13.pd in communication with the lead author he agrees that GIA use the wrong wavelength for assessing the fluorescence of diamonds.
If you take some time to study this chart from figure 3 page 85 it is very clear and apparent that 366 is the wrong wavelength / frequency. Most of the cause of blue fluorescence is from 380 to 415. The near visible to just visible violet range.
It is worth mentioning that glass windows allow this light through. The below 400nm can be blocked by some expensive glasses like those used to protect watercolor paintings and other special uses.

The message here is that we are surrounded by all sorts of lighting that excites the blue blush in fluorescent diamonds. This blue makes yellowish or brownish tinted diamond appear whiter or more colourless.

Michael - you do know that the Solarmeter 5.7 UV meter you used is the wrong one. You should have used Solarmeter 4.2, which still does not extend far enough into the visible violet, but the instrument you used simply misses the main excitation frequencies.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Web link for the article, I just skimmed it as I haven't had time to study it in depth:
https://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects

quote:
"For example, the intensity of N3 luminescence (measured at 439 nm) when excited by 400 nm excitation is approximately double that of the same emission measured at 360 nm excitation (figure 6)."

What I find even more interesting is that different colors of florescence are produced by different wavelengths of UV.
This could explain why the labs don't catch all florescence which has been commented on for years.

But one huge issue is the sample size.
I have a hard time applying the data to all diamonds with such a small sample size.
We know there is a huge variation in diamonds.
The question becomes is how representative are the samples they used?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Karl, when a diamond shows an emission line it shows that energy is being absorbed in a higher energy (smaller nm wavelength). A sample of 1 is accurate.
But yes, a diamond can have more than one emission wavelength. They do mention that.

But back to topic, N3 is the one we are interested in, the nitrogen vacancy that causes blue fluoro. It clearly derives most of it's energy from a higher wavelength than Michael Cowing is concerned about. Lexan only cuts out below 385nm and most of the blueness is coming from more visible parts of the energy.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Consider these topics in Michael Cowings own article written in 2010:

http://www.acagemlab.com/temp/CowingOvergrading.pdf

On page 42 Box A - there is virtually no excitation from the UV wavelength of 365nm GIA use to identify fluoroescence.
The excitation on the chart at that level is in the turquoise / green boundary.
The serious red zone starts at 375 and runs to 400.

Next look at figure 6 on page 43 - the lexan filter - it blocks the light energy from below 385nm according to MC- but still half the excitation is happening above that level. this is normal light that clearly is transmitted through glass and even UV filtering glass.

That means that the blue whitening effect we all know occurs is real. The one my clients and so many consumers know about - it's great. We want to make fluoro diamonds blue white and great again!

We know that GIA changed their lighting tubes and distance from lights around 15 years ago. We know they considered it and made what they thought to be the best compromise. Being one of their greatest protagonists, and trying to make them great again, as when they were ruled by Bill Boyajian - for once I think they got it right. Even though I think overall they are cheating consumers on at least 10-15% of all the stones they grade on about 15 issues. Get Bill back. Be GREAT AGAIN GIA.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

blue white

Any US dealer using that term will run afoul of the FTC.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

blue white

Any US dealer using that term will run afoul of the FTC.

Not if the diamond is D and blue fluorescent

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

blue white

Any US dealer using that term will run afoul of the FTC.

As it turned out, the FTC statute regarding blue-white inadvertently enabled what Wade and Bruton called "false color" diamonds that only looked blue-white in daylight to be called blue-white.

I attempted with the following explanation to get the FTC to correct the statute, but doubt any consideration was given.

Before diamond grading reports became so popular, there was a widespread preference in the trade for stones with fluorescence. These diamonds were called "blue-white" diamonds, and long time diamantaires can recall a time when many buyers would insist on diamonds with fluorescence. The preference began to decline after the FTC outlawed the misuse of the term "blue-white". The following is excerpted from the Federal Trade Commission's "Guides for the Jewelry, Precious Metals, and Pewter Industries".

§ 23.14 Misuse of the term "blue white."

It is unfair or deceptive to use the term "blue white" or any representation of similar meaning to describe any diamond that under normal, north daylight or its equivalent shows any color or any trace of any color other than blue or bluish.

This wording enables diamonds that are only blue-white in daylight with its strong UV and VV, but which drop below DEF color absent UV and VV stimulation to be called blue-white. This was just the opposite of what was intended.

It had the unintended effect of casting suspicion over any diamonds with fluorescence.
It's of importance to reestablish the value of the rare true blue-white (Jager) diamond that retains its "snowy white" (D-E) appearance out of daylight and fluorescence stimulating UV.

What was intended can be better worded as follows:

§ 23.14 Misuse of the term "blue white."

It is unfair or deceptive to use the term "blue white" or any representation of similar meaning to describe any diamond that, under artificial daylight balanced illumination, absent fluorescence stimulating UV and VV, shows any color or any trace of any color (e.g. yellowish or brownish) other than blue or bluish.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Here is my email to the Accredited Gemologist Association on June 3, 2016:

Today is the deadline, so at the 11th hour I submitted the following to the FTC:

Before diamond grading reports became popular, there was a widespread preference in the trade for stones with blue fluorescence. These diamonds which sometimes appeared bluish in daylight due to stimulation of blue fluorescence by the ultra violet (UV) and Visible Violet (VV) components contained in daylight were called "blue-white" diamonds.

Some of these blue fluorescent diamonds retain a high white (GIA color grades D and E) appearance under artificial daylight balanced illumination that is absent fluorescence stimulating UV and VV. Other blue fluorescent diamonds reveal a yellowish or brownish body color in illumination that is absent fluorescence stimulating UV and VV, because the blue fluorescence was masking a yellowish or brownish body color.

The intent of § 23.14 Misuse of the term "blue white" was to prohibit use of the term for diamonds having a yellowish or brownish body color in lighting where their blue fluorescence was not excited.

Unfortunately, the current wording fails in this regard, because the "normal, north daylight" with its strong UV and VV component is masking with blue fluorescence the yellowish or brownish body color :

§ 23.14 Misuse of the term "blue white"
It is unfair or deceptive to use the term "blue white" or any representation of similar meaning to describe any diamond that under normal, north daylight or its equivalent shows any color or any trace of any color other than blue or bluish.

The following proposed rewording fulfills the original intent:

§ 23.14 Misuse of the term "blue white."

It is unfair or deceptive to use the term "blue white" or any representation of similar meaning to describe any diamond that, under artificial daylight balanced illumination, absent fluorescence stimulating UV and VV, shows any color or any trace of any color (e.g. yellowish or brownish) other than blue or bluish.

 

[whitewave]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

24 years after buying it, I discovered my original engagement ring has strong fluro. We paid $1,000 in 1993 for this uncertified H color, I1 .75 round diamond: I was making $15,000 a year teaching and DH had no income at the time (post grad). We went to a "good" jewelry store and they showed us this and it seemed white and sparkly to me, so that was that. (I was always confused because I remembered the salesman saying the color was close to a D and when I finally broke out the insurance appraisal and saw it was an H.... it never made sense to me)...



LED light:


Outside on a overcast day:


I just sent it off to be set as a pendant. I'm trying to follow along on this thread. It is interesting.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

24 years after buying it, I discovered my original engagement ring has strong fluro. We paid $1,000 in 1993 for this uncertified H color, I1 .75 round diamond: I was making $15,000 a year teaching and DH had no income at the time (post grad). We went to a "good" jewelry store and they showed us this and it seemed white and sparkly to me, so that was that. (I was always confused because I remembered the salesman saying the color was close to a D and when I finally broke out the insurance appraisal and saw it was an H.... it never made sense to me)...


I just sent it off to be set as a pendant. I'm trying to follow along on this thread. It is interesting.

Very cool whitewave. It does look very white in the sunlight shot. And because the light is diffused by the clouds, the stone also looks very bright.

How fun that your special stone became a little more magical after all those years!

 

[whitewave]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks, I call it my hot mess.

Interesting article about fhe foxfire diamond and its fluro qualities (excuse if this has been posted)

http://insider.si.edu/2017/01/diamonds-eerie-glow-earns-fiery-name/

 

[Garry H (Cut Nut)]

This GIA (G&G 2013) graph shows how the frequencies (red line) of UV and visible violet cause various frequencies emissions of light (blue line). Note the strongest effects are from 380 to 400nm and 415nm. GIA grades fluorescence with 365nm – the only UV light source available decades ago; they will probably change soon based on what I read in their patents.
Note that at 365nm there is a lot less blue fluorescence caused. Note also that 365nm will mostly be chopped out of sunlight by windows, and none comes from normal lights.
But the 380 to 415nm comes through windows.

 

[Garry H (Cut Nut)]

This experiment shows that light that causes the strongest fluorescent reaction in diamonds (380 to 415nm) passes through windows. These inexpensive visible and near visible UV LEDs (frequencies around 390-420nm) are shown with no screening on the left, and screened on the right by ordinary glass of 5mm thickness - actually my glass wine decanter.

 

[Garry H (Cut Nut)]

This photo shows a different also cheap LED with and without screening by two 3mm sheets of Lexan polycarbonate (the exposure and aperture are the same in both photos).
The visible violet we see is generally above 400nm and this passes virtually unimpeded through glass and Lexan - this light contains the very powerful 415nm radiation that we can see and creates a strong violet shade in a blue fluorescent diamond.

Lexan totally blocks UVA like the 365nm UV radiation that is (wrongly) used to grade the strength of fluorescence by labs like GIA. Wrong because it was once the only easily made long wave UV, and wrong because it does not cause much of the blue fluorescence we observe in a diamond. It is mainly used by gemologists to ID various gem types and separate synthetic gems from natural etc/.

 

[drk14]

This GIA (G&G 2013) graph shows how the frequencies (red line) of UV and visible violet cause various frequencies emissions of light (blue line). Note the strongest effects are from 380 to 400nm and 415nm. GIA grades fluorescence with 365nm – the only UV light source available decades ago; they will probably change soon based on what I read in their patents.
Note that at 365nm there is a lot less blue fluorescence caused. Note also that 365nm will mostly be chopped out of sunlight by windows, and none comes from normal lights.
But the 380 to 415nm comes through windows.

Garry,
I disagree with your interpretation of this graph, assuming it is an adaptation of Fig. 3 from the Luo & Breeding (2013) paper that you referenced in Post #522 above. In this 2D plot, the emission curve (blue line on the right) is the emission curve for excitation by a 325-nm UV laser. The absorbance curve (red line on the left), on the other hand, shows which wavelengths are absorbed (i.e., neither reflected not transmitted) by this stone (Sample #2), and does not necessarily mean that the corresponding wavelengths excite any fluorescence. Moreover, those absorbed wavelengths (in the red curve) that do produce fluorescence, do not necessarily emit at the wavelengths depicted in the emission spectrum, since that spectrum is specific to excitation at 325 nm.

I haven't examined enough of this thread to know whether I agree or disagree with your main point, but unfortunately, I do not think that this particular graph can be used as evidence to support your argument. The 3D fluorescence excitation/emission spectra are more suitable for answering the kind of questions posed in this discussion.

 

[Garry H (Cut Nut)]

Dear DRK14,
Correction. There is no laser light source in the Thermo Aminco Bowman II spectrascope. Luo et al used it's Xenon energy source in the 300nm to 750nm range with filters (Fluorometry system).
Is that your only possible objection?

 

[OoohShiny]

Interesting article about fhe foxfire diamond and its fluro qualities (excuse if this has been posted)

http://insider.si.edu/2017/01/diamonds-eerie-glow-earns-fiery-name/

That is so cool, thank you for posting it

 

[drk14]

There is no laser light source in the Thermo Aminco Bowman II spectrascope. Luo et al used it's Xenon energy source in the 300nm to 750nm range with filters (Fluorometry system).

Garry,
My original comments (post #536), as well as this response, are based on the assumption that the graph shown in your post #533 is based on measurements acquired using the methods described in Luo & Breeding (2013), and that it is equivalent to the graph that appears in the top right panel of their Figure 3. The two graphs are not identical, but the main difference appears to be that the axis limits have changed.

The Materials and Methods section of the Luo & Breeding paper explain that they have employed three distinct measurement techniques to evaluate the optical properties of diamonds:

1. 3D Luminescence Spectroscopy: Uses the AMINCO-Bowman Series II (ABII) spectrofluorometer to acquire 3D excitation/emission spectra (such as these).
   
2. Photoluminescence Spectroscopy: Uses a Renishaw inVia Raman microscope to excite samples using lasers at one of the following wavelengths: 325nm, 488nm, 514nm, 633nm, or 830nm laser, and collects a scan of the emission spectrum for the chosen laser excitation frequencies.
   
3. Absorption Spectroscopy: Uses an Ocean Optics integrating sphere to produce a full-spectrum (UV-Vis-IR) excitation and measures the absorption of each wavelength by the diamond using an Ocean Optics HR4000 CCD spectrometer.

My point is that the graph in question was not measured using the ABII spectrofluorometer (Method #1). The left side of the graph is the absorption spectrum acquired using the Ocean Optics integrating sphere & spectrometer (Method #3). The right side of the graph is the Raman spectrum acquired using 325-nm laser excitation (Method #2).

Note also that the type of absorbance graph produced by the integrating sphere experiment is not equivalent to a fluorescence excitation spectrum. Photons that are absorbed do not necessarily produce fluorescence, as the energy can relax via other means or be re-emitted via Rayleigh scattering.

So, I stand by my original comments.

Is that your only possible objection?

Since you ask, I also have some quibbles with your photographs of LED sources, but I will leave that for another day...

 

[Texas Leaguer]

drk,
Would you mind telling us a little bit about your scientific background? You are extremely adept at slicing and dicing this stuff. Many of us struggle to fully comprehend some of the highly technical studies.