Thanks very much Dear Thomas.

I am going to do it immediately

Hi

I saw untypical obsidian in Italy near Napoli but it wasn't in pyroclastic materials. And it was more white than green.

Did you download a photomicrograph?

Hi, Laetitia,

Thanks for your answer.

Yes I made it and it shows a glassy mesostasis with plenty of phenocrysts. I am still looking for a name for such particles.

Hi

perhaps this paper could give you ideas...

http://www.clays.org/journal/archive/volume%2047/47-6-708.pdf

Thank very much Laetitia !

I will have a look and see.

Green in colour? From the photo... Uh

The natural color is yellowish

No dear Thomas.

There is no evidence of fumarole in the region.

Thanks. I think it may be the effect of hydrothermalism as suggested by Prof James White.

Dear, Thomas

Prof James White suggested that the possibility, given the pale color, is that these are some sort of hydrothermal mineral, like chalcedony. From the thin section proposed, he concluded that it does have a glassy mesostasis – some sort of glassy volcanic rock with a lot of phenocrysts.