Hello,
I almost die, when I was extracting this ammonite from wall of abandoned limestone quarry.
So, that's my very first stone preparation, of 200 mm (7,8") ammonite (Perisphinctes), which I found near my hometown - Kraków, Poland.
OK, I know, it's not so big, but the largest I have ever found.
As You can see I got carried away, so it's half natural specimen, and half carving.
Preparation I done with Dremel Engraver and some chisels I made from old files. I enjoyed it well