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Unusual Hauyne Crystals from Afghanistan

This specimen is from Sar-e-Sang, Badakhshan, Afghanistan. The specimen contains 3 fluorescent minerals, gonnardite ((Na,Ca)2(Si,Al)5O10 · 3H2O), diopside (CaMgSi2O6) and hauyne

((Na,K)3(Ca,Na)(Al3Si3O12)(SO4,S,Cl)). The gonnardite and diopside ID’s were confirmed with XRD analysis. The blue hauyne crystals are mostly non-fluorescent except for fluorescent veinlets in the crystals that glow orange. Not sure on how these veinlets formed. Possibly during crystal formation, the crystals were fractured and the rapid change in pressure and temperature changed the chemistry and /or lattice of the precipitating hauyne. The ideal formula for hauyne is (Na3Ca(Si3Al3)O12(SO4)). The substitution of potassium, sulfide, and chloride as well as changes in the relative amounts of sodium and calcium can change the properties of hauyne. The longwave UV fluorescent spectra of the hauyne show multiple peaks caused by di-sulfide ions substituting for sulfate in the hauyne structure. Lazurite, the blue mineral in lapis lazuli, is a sulfide-rich hauyne that is non-fluorescent. The blue, non-fluorescent mineral in this specimen is not lazurite. It is not opaque, the blue color is lighter than true lazurite and is does not make a blue mark when rubbed on a streak plate.

The first picture shows the specimen illuminated by longwave UV light. The hauyne fluoresces orange, the gonnardite fluoresces white, and the diopside fluoresces gray.

The second picture is a false color infrared image of the longwave fluoresce. This picture is created by assigning green fluorescent light to blue, red fluorescent light is assigned to green and infrared fluorescent light is assigned to red. The hauyne appears yellow in this image because it fluoresces red and near infrared. Gonnardite appears as a pale blue color and diopside has a pink color.

The third picture shows fluorescent spectra of the three minerals. The multiple peaks in the hauyne spectrum are caused by the di-sulfide activator. Titanium is probably the activator of the diopside fluorescence. I do not know the activator for the gonnardite fluorescence.

The fourth picture shows the specimen illuminated by shortwave UV light. The hauyne in non-fluorescent in shortwave light. The gonnardite fluoresces blue-gray in SW and the diopside fluoresces bright white.

The fifth picture is a full-wave image of the specimen (LW + MW + SW). The sixth picture is a false color infrared image of the full-wave fluorescence.

The seventh picture is a white light image of the specimen.

The last 2 pictures are closeups of the fluorescent veinlets in the blue hauyne crystals. (LW and white light)

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Oct 31, 2022

I did EDX on such a specimen. It turned out that the fluorescing interior is actually afghanite. In the end stage of crystallization it is covered by a layer of lazurite (the real one according to the latest IMA status). The combination was described by Chukanov (2020), which made me do EDX on the samples to check.

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