Ammonites

Ammonites are a group of extinct marine cephalpod mollusks, closely related to the Nautiluses that are alive today and are in the distant family of modern Octopus, Squid and Cuttlefish. Just like modern Nautiluses the Ammonites were known for their unique spiral shell making it a gorgeous unmistakable fossil today. They existed during the Devonian period about 400 million years ago. Ammonite fossils are primarily made of calcium carbonate but depending on region they can also be replaced by sillica or pyrite as well which are a true site to see. They can be found all over the world and are quite affordable due to their abundance for a fossil making it a must have for any fossil collector

Hardness: 3 – 4
Composition: (CaCo₃) or SiO₂ or FeS₂