My Christmas Present

This is my Christmas present from S. It's some rocks. But these are special rocks - you put them in a bowl, and cover them with (distilled, white) vinegar, and then you wait. And wait some more.
When all the vinegar has evaporated, the rocks grow some interesting structures, that look a bit like popcorn, and this mimics some geological process - but taking less time, by a factor of a couple of million.
I've just noticed that the picture looks like an arty black and white shot. It's not, it's just black rocks, and glass on a white background.

(And the stripey bits around the edge of the bowl are compression artifacts, and would get your picture rejected by www.istockphoto.com).

Actually, if you type "popcorn rocks" into Google (or your search engine of choice, I imagine - I've just not tried any other, because I'm not, errr..., well let's just say not the kind of person that uses other search engines, and leave it at that. People that use Google know the kind of person I'm talking about) you can find out all about them. I'll take another picture when they've grown. If I remember.