Strong Blue Fluorescence

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Jan 2, 2003
I am interested in a diamond with a pretty good graiding 1.21, E, VS2, 62.9%, 57%. The one thing holding me back from purchasing it is it's strong blue fluorescence. This diamond is for an engagement ring so I'm not looking at it as an investment for future resale. How much will the fluorescence impact the beauty of this diamond on during normal day to day activities (in daylight, shopping, resturants, movies)? Is it even noticeable to the human eye without UV lighting (black light)? Does anyone have any experience with strong blue diamonds?




Sep 3, 2000
Tke the diamond out into bright sunlight along with a similar color and cut diamond that has negligible or no UV fluorescence. Make a comparison yourself to see what it means to you. The strong fluorescence will likely show itself in coloration or in a bit of cloudiness when the stone is in sunlight. If you can see this effect, then YOU decide.

The price will likely already reflect the 2 to 6 percent lower mrket price for this fluorescent effect. Expect to pay a bit more without UV fluorescence.

There is no reason to avoid these stones, but you must become aware of what is inherent in the stone before you buy it.


Aug 15, 2000
Observing fluoresence ....

I would also suggest that you use a small piece of LEXAN, which can be purchased from most plastics dealers for a few dollars.

Use 1/4 inch thickness..... Hold the Lexan between the light source ( sun ) and the diamond. Observe the stone without the Lexan filter, and then using it. You'll see the difference and affect of the fluoresence a lot easier.

Lexan removes the UV component from travelling through to the stone, so when you take away the filter you'll get a far truer image of how much the fluoresence affects the appearance of the diamond.

Also don't rely on the stone having strong fluoresence to have an affect on appearance. I have seen stones with medium fluoresence display an affect on the diamond.

Hope this helps.



Nov 24, 2002
I have owned an SB fluor ideal cut stone and returned it after seeing it in many lighting conditions. Sunlight and some incadescent lighting conditions will give the diamond a blue/violet tint and perhaps make it appear slightly opaque (as any glowing object might) at certain angles.

Under other lighting, the diamond may have even pinkish or greenish soft glow but very white in most lighting conditons (I had a G). In most lighting conditions (containing some UV) it will definitely show up whiter face up and from a profile. Yes, even in the profile view it looks white to slightly blue in incadescent lighting. The G color stone I have now with faint fluor appears very slightly yellow like a normal G from the side.

I don't know if it's due to other variables (the only variable other than fluor bieng proporiton which was nearly the same except for a slightly shallower crown (34.3 versus 34.1), a slightly overall deepness (61.5 versus 60.9), and a slightly thicker girdle (but still medium for both) on a stone without fluor , but the stone with strong fluor had very intense white flashes of whereas the stone with faint fluor was dispersing bold colors and white light like mad in sunlight. In a dark room with point lighting, the SB fluor stone looked exceedingly white sparkly with a dark background (not white as in brilliant but like white fire) wheareas the stone with faint fluor appeared slighly less intensely sparkly with a lighter body color and some fire fire. The SB stone looked darker and more contrasty while the faint flour stone looked brighter and firey (almost no fire in SB fluor). The light leakage of SB stone was also nearly nil whereas the faint fluor stone had some peripheral leakage and slight table leakage (used an ideal-scope). Also, the faint flour stone had more distribution of black spots betwee arrow heads and arrow shafts while the SB fluor stone had only black arrows and smaller black spots between arrow heads, though both were H&A patterns. The color and clarity were the same for both (VS1s with crystals and feathers). Both are AGS ideal cuts with HCA scores 1 and 1.1.

So the bottom line is that it appeared blue/violet in the sunlight that all my buddies could see without dubiety and possibly had less fire. Other factors such as symmetry patterns, leakge patterns, and even the minute proportion differences could have affected fire so judgement on effects on fire are tenous.

My personal opinion is that SB fluors definite blue/violet tint is undesireable if one is wants a colorless stone. If one wants a chameleon, that is another story.

Even the faint fluor stone has some very very pale sky blue (not violet) face up color only in very strong sunlight but it is seems to have no effect on dispersion and blinding light return. I've also read that colorless diamonds naturally appear slightly blue so I can't really say if faint fluor is causing this and from what I've read faint fluor should have no effect. In any case I find this nearly undetectable tint pleasing whereas in SB fluor it's just so very blue/violet which makes it look like a blue/violet diamond.

Loss of transparency is touted rare, so the color in sunlight should be more of a concern for those considering SB or perhaps even med fluor.


Dec 27, 2002
Interesting post Hbright,...
Bottom line is that if you start picking the diamond properties apart and look for top quality gem, and look at diamonds like "D", "Flawless"
and "Ideal cut" strong blue fluorescence wil not be desirable.
If you are buying stones of regular cut proportions, and low color fluorescence may help your "J-K" colored diamond to appear whiter and that is a good thing,...
The trully dificult part in interference of strong fluorescence is when grading natural fancy colored diamonds. There you see the different types of fluorescence to trully ruin the beauty of some othewise stunning gems. You may have a Fancy light Yellow with strong Blue fluorescence and the diamond will appear almost colorless or like a dull "K" colored white diamond under certain light. Another interesting factors are yellow or green fluorescence. Those properties are part of creating the natural chameleon in fancy colored diamonds witch is very desirable by colectors.
Diamond can appear like strong canary yellow and under different light can look green or light blue ..
Bottom line weather you buy high quality colored diamond or white (colorless) Strong fluorescence is undesirable. When buying lover colors budget stones. fluorescence may be desirable or negligeable. As far as faint fluorescence goes, You would have to be vizard to be able to see it with your naked eyes,...
The value of diamond is usually not effected by faint fluorescence.
good night
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