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Messaggeria in lingua italianafrom top of Etna

1st May 2016 06:05 UTCGeorg Graf

04657540016029654483793.jpg



Buongiorno a Tutti,


found this white crust on volcanic rocks on the top of the Etna Mountain, Sicily. By the way of occurence, I think, it´s natural. What can it be?


Any thoughts are appreciated.


Thanks/Grazie in advance, Georg

1st May 2016 13:30 UTCReiner Mielke Expert

Is it soluble in water?

1st May 2016 23:02 UTCPaul Brandes 🌟 Manager

Your photo isn't the best Georg, but to me it looks like a piece of volcanic cinder that got blown out of Etna during one of its eruptions. Does it seem lighter in weight compared to other rocks of the same size?

2nd May 2016 00:57 UTCReiner Mielke Expert

I think he wants to know what the white crust is.

2nd May 2016 05:06 UTCGeorg Graf

Hi Reiner, hi Paul,


the white crust is neither in cold nor in hot water soluble.


Georg

2nd May 2016 08:17 UTCAlfredo Petrov Manager

Possibly a crust formed where acidic gases altered the surface of the rock. It could be composed mostly of opal, alunite, kaolinite, or...? Very common around volcanic vents. But you need an analysis, as it isn't possibly to definitively ID non- or poorly crystallized crusts from a photo.

2nd May 2016 13:35 UTCReiner Mielke Expert

I agree with Alfredo.

2nd May 2016 20:02 UTCGeorg Graf

Thanks you all for your responses. (Chemical analysis will need time.)


Georg

9th Jun 2016 17:58 UTCŁukasz Kruszewski Expert

I agree - a bunch of species may be "responsible"; I was thinking about gypsum, anhydrite and bassanite - especially the latter one. But its impossible to confirm without XRD and/or chemistry.
 
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