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Green hauyne and photochromic sodalite, Koksha valley, Afghanistan



Specimens like this are mostly sold as green and purple sodalite, but most are massive pieces. This piece contains part of a crystal that reveals what happened. The green is the first to crystalize. In a later stage it is covered/surrounded by a layer of photochromic sodalite. The green is fluorescing very vivid orange (365 nm), the purple a lot weaker and it also shows the typical white fluorescence (310, 275 and 255 nm) and afterglow. The spectra tell us more. Both parts show the orange fluorescence from the S2- ion. But the green mineral has the typical hauyne spectrum, while the purple shows the sodalite spectrum. The dashed line is the white Ti3+ fluorescence. The hauyne is green. This is the result of the simultaneous presence of the S3 chromophore giving a blue colour and the S2 chromophore giving a yellow colour.

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