Yes really interesting!! These ones must be rejects as in the snap I saw they were almost all completely round ?? 

Are we looking at something life size or magnified?

lol Paul, I know you know.

Sure hints are allowed.
Yes intrepid, this is how you would see them. Not in New Zealand though, well not to my knowledge.

Look at the background.
What are they in/on.
This will help you guess

My first impression is ice/snow on volcanic rocks.

My first impression is ice/snow

Very Hot.

Not rock, try again on the background.

Edit: 2.30pm

Hard one this but interesting.

"We weren't sure what they are called but we found this explanation that we think fits. What we think happened is this: Foam floating about on the water started to freeze, probably at night. Bits of frozen foam got swirled around in an eddy, and became roughly circular. Perhaps each disc grew when smaller pieces of unfrozen foam struck the disc, adhered and then froze in place.

The raised rims are undoubtedly due to the collisions but what about the inner lines? The air temperature was colder at night due to the clear-sky conditions but warmer in the day, meaning the discs may have grown at night, then during the day, when the discs softened in the sun, further collisions between the “pancakes” caused the rims to be pushed up. The next night further growth would have occurred, followed by a new rim the next day."

More pictures etc here. Worth having a look at:

http://www.riverdee.org.uk/blog.asp