re: But, just... maybe.
Maybe, just maybe, this silica was formed not just under hydothermal conditions, but something indicative to this:
http://jsedres.sepmonline.org/cgi/content/abstract/67/5/805
Let's say that the silica is a combination of geothermal activity combined with it's formation in a lake environment.
(Bare with me, I'm just thinking here.)
Yes, we need to hear more.
