Hi Pavel,

Excellent information from you, thank you. I myself have only minimal experience of volcanoes, mostly at the Italian ones. I spent a month at the La Fossa crater, and was fascinated by the sal ammoniac, getting some good pictures of its crystallisation. I hadn’t realised that it only occurs there and that other volcanoes don’t produce it in quantity. Which is why I posted the question. I bow down to your certainty of identification.

Cheers

Roger