origin of yellow color in danburite

[mogok]

Hello,
One question that trouble me from times to times: Does somebody knows what is the origin of the yellow color in Danburite?
Very fine quality yellow Danburites can be found in Mogok, Burma, in Madagascar and possibly in Mexico.
They dont show any spectrum...
Can anybody give me any verified information about this?

Thanks

 

[mike04456]

I checked my library, and all I could find was a brief 1986 note from GIA about having detected a 595 nm line in the spectrum, which they attributed to unnamed rare earth elements. Danburite commonly has iron and magnesium as impurities; both are known to cause yellow color in other gems, although presumably if either was the cause there would be spectral evidence of it.




Danburite is such a rare gem mineral that it's entirely possible that no one has ever bothered to determine the cause of color.

 

[valeria101]

As far as I know damburite can be yelow (till orange) and rarely pink aside the rather non-rare whites. Anything else?

 

[mogok]

Hi,
Thanks for your quick answers!

Law gem: We are exactly at the same point! So my question...
AnA you are right:

Colorless is the common color,
Pink, ok but I've never seen any as to my knowledge they are found only in Mexico and Japan (very very rare)
Yellow comes in Mogok from light straw yellow to very bright yellow (Gorgeous when cut in gems) I've never seen any brown or orange yet in Mogok...

Anyway as I would like to get this info as its clearly missing in my data and explanation pages about danburite... Aarg!

Thanks to all of you,

 

[valeria101]

Lawgem, is the article you have available online (or in electronic format) anywhere? What is the citation... if you get time for this.

 

[mogok]

To put some color in all these words:

Here is a fine Mogok yellow danburite crystal. This stone was probably from the Pyant Gyi area is the east of Mogok which is also the area in which we can find the best red spinels and some very nice blue apatite.

Enough words! ...

 

[mike04456]

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On 1/23/2004 11:45:48 AM valeria101 wrote:






Lawgem, is the article you have available online (or in electronic format) anywhere? What is the citation... if you get time for this.

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It's in the Spring 1986 issue of Gems & Gemology, p. 47. GIA has put a couple of G&G articles online, but old stuff like that is not, to my knowledge.

 

[Richard M.]

Mogok, LawGem

I can't say for certain but didymium appears to be the probable suspect. Anderson & Payne list yellow danburite with yellow apatite and sphene which all show didymium lines in the yellow at around 584 nm. and possibly in the green at 527. As they state:

"Normally it is only apatite among the regular gem minerals that exhibits the didymium lines at all strongly, but a number of other minerals may be found which sometimes show vestigal traces of the yellow complex in their deeper coloured specimens. These include danburite, sphene, fluorspar, idocrase and calcite, in all of which the lines are all very faint and elusive, and often totally absent."

 

[mogok]

Hello Richard,
Thanks for this information, I will enquiry about that.
By the way do you have the exact reference of your sources about didymium? To my knowledge didymium is not an element but a mixture of praseodymium and neodymium which are 2 rare elements. It was believed to be an element until 1885 when it was split into this 2 elements.
Thanks again for this post.

 

[Richard M.]

Mogok,

All I know about didymium is the fascinating spectrum it creates in apatite. The only danburite I have on hand is colorless material from Mexico. My source is the 1998 edition of "The Spectroscope and Gemolgy" [Ed. R. Keith Mitchell] by Basil Anderson and James Payne, pages 206 & 251.

 

[mogok]

Hello Richard,

Do you mean that you have been able to see the Didymium spectrum in this colorless danburite? It sound weird to me as if the stone is colorless there should not be any absorbtion spectrum (or your stone is not that colorless as that).
I'm very conserned about the origin of the color in the bright golden yellow danburites we can find sometimes (If lucky) in Mogok. I really love these stones and I would like to provide some more information about it to gemwow.com visitors.

All the best, and thanks for your help...

 

[Richard M.]

Hello Mogok,

No, I meant that I could NOT check for spectra in my samples because they are colorless. If the color of Myanmar danburite is as rich as the images you posted, it should be very beautiful after cutting, which should intensify the color even more.

 

[mogok]

Hello Richard,
Well thats what I was suspecting! For the color of these danburites, you are right: Fine quality danburites are gorgeous gemstones when they are properly cut.
I dont have currently any picture of any fine cut danburite... I've seen some of them but could get a pic of them. The only one I have is from a stone that I bought long time ago for its typical inclusions: "Hollow tubes" that are typical in Mogok danburite. This stone has a straw yellow color which is already not bad but not the finest we can encounter in Mogok material but in this stone the tubes were so visible that the stone was just great to my eyes!
Have a look...

 

[strmrdr]

Mogok,
That Is one neat looking stone.
I can see why you like it.

 

[mogok]

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On 2/18/2004 10:10:22 AM strmrdr wrote:

Mogok,
That Is one neat looking stone.
I can see why you like it.

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Well that a point. Generally speaking I really simply "hate clean stones"... This came to my time as gemology student in GIA... Grading diamonds "flawless", "internally flawless" or even VVS was so time consuming and "pain in the neck" that the more I was sudying the more I was in love with stones that had inclusions.
Some people still stick to call inlcusions "defects" or "flaws"... For me they are just not: They are very desirable birth marks.. so important that they are the first thing I check in a stone when I go to buy: If they please me then I look for the rest!

Natural inclusions are tale telling birth marks that are very usefull to identify the stone, its possible origin and if the stone was or was not treated.
They can be also very very beautiful!
For me there is the global apparent beauty of the stone which is visible to everybody but if a stone has also an internal beauty, more intimate, just visible with the loupe for its owner pleasure then I dont see any reason for this stone to have less value than a "pain in the neck" clean one!
I really love Mogok rubies, sapphires, spinels as they have beautiful inclusions... They are the secret gardens of these gems... They are just perfection as they are more reliable than the report from a lab: They speak to you and if you take the time to learn about your stone then you understand than your stone is not the same as the stone from someone else.
People have value as individuals because they are unique and different to each other. Fine gemstones are the same! I love people not for their qualities (everybody love them...) but for their bad sides because I know that I can accept these imperfections... For gemstones its exactly the same. Perfect people does not exist... They are suspect! Gemstones are just the same...

Well May be I spend too much time in Burma with these Mogok people that love their stones for more than 1000 years!

All the best,

I have bought this danburite because of these very fine inclusions and believe me or not: I gave this stone to a show room last year. It was sold the day after!

 

[Richard M.]

Hello Mogok,

What neat inclusions! Thanks for posting the image. Like you I often buy stones with interesting or unusual inclusions.

I agree that the diamond trade’s relentless emphasis on the concept of “flawless” has unduly influenced the public’s understanding of inclusions in colored gems. True, there are a few gems that are prized for their inclusions like star stones, cat’s-eyes, rutilated quartz and demantoid garnets with “horsetail” byssolite. Of course too many and the wrong kinds of inclusions are not desirable!

 

[mogok]

Hello guys,
That a picture of fine "straw yellow" Mogok danburite. The color is classic and the stone is very nicely cut. But more saturated yellow are possibles...
I will get you one photo of what I mean...
And still this color origin uncertain!
Anyway...
All the best!

 

[valeria101]

What type of test (on typical gem lab equipment or otherwise) would answer your question about color origin ? This sounds like a nice challenge already

 

[mogok]

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On 2/19/2004 9:59:02 PM valeria101 wrote:

What type of test (on typical gem lab equipment or otherwise) would answer your question about color origin ? This sounds like a nice challenge already

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Well I think that its not a test that someone has to do but a complete study. Tests can help to make supposition but then proofs has to be found.
I think that this could be a possible subject for somebody going to spend 3 months in Nantes (France) to get his DUG along with Doctor Emmanuel Fritsch. I think that this is the only place in the world in which a gemologist can go to study about all the advanced gemological and laboratory analytical equipment and do a 3 months research work.

This subject was one of my possible think for next winter, or this is something I can give to somebody who would like to go there to do it...

My purpose with this question is to found if somebody has already studied that...
Most of my reference when they mention yellow danburite says: origin of color unknown.

Ok Danburite is not ruby or diamond... So why to spend time and money searching about the origin of color here... But who knows?

All the best,
Thanks for your help!