Ammonites fossil , a ribbed spiral formed shell and they begin their life as tiny plankton and quickly grow a strong protective shell. These ammonites created their shells with a mix of a particular sediment and this combination produces the beautiful surface colourings. Ammonite fossils are formed when the remains of the animal become buried in sediment which later solidifies into rock.
Beautiful polished Ammonites are 110 million years old .  4.5cm roughly each other be may vary slightly. 🧡