Can dispersion colors be "muddy"

[Garry H (Cut Nut)]

This originated in another thread, but was off topic.

It is a geeky idea that stress or poor symmetry can cause muddy of not really vibrant dispersion colors.

This is the first time I ever noticed the effect. I took this photo today. Note that some of the colors are muted - what I was taught are second order diffraction colors.

 

[Capitol Bill]

Garry,
The particulars of this stone aside, wouldn''t very strong fluorescence cause this kind of "muddy" dispersion?
Bill Scherlag

 

[Maxine]

It almost looks the way "Mica" did....that stuff that peeled....used to find it in North Jersey......

 

[oldminer]

Dispersion in diamond would not generally mke a stone look muddy. In some older diamond simulants and in Moissanite, dispersion is greater than diamond and may make the stone look less transparent, or muddy. There is dispersion in diamond, but the way diamonds are cut does not seek to maximize the effect.....most of the time. I suppose one could do it intentionally just to disprove the generalization .

 

[Michael_E]

I think that you''re pulling the wool over our eyes here Garry. You never said that this stone is a diamond and I don''t think that it is. This looks for all the world to be a calcite or maybe a sphene. Something with very high birefringence. This would also explain the "muddy fire" due to spectral interference. Come clean on this one. That''s not a diamond, it''s a calcite isn''t it ?

 

[JohnQuixote]

Bravo Michael.

 

[Garry H (Cut Nut)]

Actually Ana got it first on another thread - but I think Michael desreves 100% kudos too

The dispersion colors are indeed mixing because of calcites very strong double refraction. this stone is on display at the Smithsonian.
Credits to http://www.gwydir.demon.co.uk/jo/minerals/calcdref.htm for the image

Oh, and BTW note the pale muddy colored dispersion in this image - second oreder type dispersion like you often see in thin film difrection when water spills on olli at a gararge

 

[Capitol Bill]

Garry,
Since I was privy to the stone being calcite all along, it obviously wouldn''t have been fair for me to guess. But I have seen a similar effect (not the facet doubling, but the "muddy" dispersion) produced by diamonds with very strong fluorescence. Ana & Michael E should be commended for their identification skills.
Bill

 

[Serg]

re: "It is a geeky idea that stress or poor symmetry can cause muddy of not really vibrant dispersion colors."
"Oh, and BTW note the pale muddy colored dispersion in this image - second oreder type dispersion like you often see in thin film difrection when water spills on olli at a gararge
"

Can not see any conection between poor symmetry and interference