I'm reading the Casteret books at the moment, several times when describing ice formations in caves he mentions ice crystals that "may be fossilised". What exactly does this mean? He seems to be describing them as still in ice form. Surely old ice is still just ice? Or can some sort of mineralisation take place?

I suspect that it's just flowery writing for "old ice". Casteret was not one to use a simple word where several sub clauses would do.

graham said:

I suspect that it's just flowery writing for "old ice". Casteret was not one to use a simple word where several sub clauses would do.

Click to expand...

Probably.  At the time he wrote Ten Years Under the Earth the study of ice deposits in caves was in its infancy.  So anything which appeared to have been there for a long time would have been referred to as "fossilised" ice, especially if it showed evidence of erosion.