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 Post subject: Re: Cause of adularescence in Moonstone
PostPosted: Fri May 13, 2011 4:30 pm 
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diataon wrote:
"the planar shape of scattering in opals give rise to thin-film interference effects in the scattering."

I think I'll just leave than one!!


Ah yes, should read "planar shape of scatterers..."

Interleaved planes of scatterers cause the interference and diffraction effects that you cited from one text as giving rise to the colors seen in opal.

Frank... maybe. :D


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 Post subject: Re: Cause of adularescence in Moonstone
PostPosted: Wed Apr 14, 2021 2:15 pm 
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Barbra Voltaire, FGG wrote:
pandora wrote:

Those blue labradorites are beautiful - what is the location - and how do they compare in performance with the 'moonstones'. I have a particular fondness for the very transparent 'rainbow moonstone' labradorites, they're not that easy to find.



The labradorite moonstones are coming from India. They are the finest examples I have see in what we loosely call moonstone. :D

The adularescent effect is not a mystery in either the orthoclase/albite nor labradorite.

In the case of orthoclase, the effect is caused by the interference of light resulting from layering with albite (end member of the plagioclase series). If the layering is thin, light interference produces a blue schiller. If the layers are thicker the sheen appears white. In order to get the best effect, the stone should be cut so that the plane of the base of the cabochon lies parallel to the plane of the layers.

For further information on the physics of the phenomenon,see:
"Rayleigh Scattering", George Rossman and E. Fritsch, G&G, Summer 1988

Hope this helps

The effect can also be seen in a glass of watered down milk. The glass must be clear and the milk watered down enough so that it is translucent. The milk has a bluish tint when illuminated in reflection. When illuminated in transmission, light seen coming through the milk looks reddish.


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