3d model of a nice ammonite fossil sink seen on internet. It's not commercial, use it only for yourself. Don't sell your make nor the stl! The designer of the original thing have all the rights.
There are 2 files, one is the sink while the other is a negative of the ammonite used as a mold.
Scale it as you want (xy or z). As it is, the inner diameter have 50mm.