re: "I found a nice discussion about the frost here, of all places. :) "
That was an interesting thread and I'm sorry I missed it.
About that 'pyramid'. It reminds me of a a similar one I've seen in the West Thumb Geyser basin in Yellowstone when it isn't submerged. (I've never been to Yellowstone yet and I'll have to thank Google for that one.)
Best.
