Stone or fossil?

[Gust]

Hi all,
I found these two stones with strange patterns and was wondering if they may be fossils.
Stone 1 looks a bit like a flattened shell.


Size:
Stone 1: 2.2 x 3.2 x 0.2 cm

Stone 2: 2.3 x 2.2 x 0.3 cm

[sjaak]

Ironstone (limoniet).