A fossil is a rock containing the preserved evidence of once living animals or plants. Fossils are found in sedimentary rocks (e.g., limestone, chalk and sandstone) as the fossil forms when the animal (or plant) is buried in sediment. Its soft parts rot away but any longer lasting hard parts will gradually be mineralised and turned to stone.

All ammonite species are long since extinct, their nearest equivalent today is the nautilus found in the Pacific Ocean. Ammonites swam in seas in many parts of the world and evolved over time into many variations of the basic pattern of a coiled shell. The smallest were about 1cm across right up to massive species reaching over 1m in diameter. Their era lasted from approximately 400 to 65 million years ago. This means that ammonites swam in seas when dinosaurs roamed the land.

Their shells were divided internally into chambers. By regulating the gas in the chambers, the ammonite could move up or down. It swam backwards, probably using jet propulsion(water forced through its 'mouth' at high pressure).

Most species lived in relatively shallow coastal waters at depths of 50-200m. The largest types probably lived in the warmer seas. They were carnivores, pulling food in with many 'arms' around their 'mouths'. The ammonite's body only occupied the final outer chamber of coiled shell.

Ammonite shells were made of aragonite. Some species show complex wavy or zigzag patterns on their outer shell. These are the edge of the walls (septa) which separate the many chambers – and are used in the classification of ammonite.

Palaeontologists are not entirely sure why ammonites, which once held a dominant position in our oceans, became extinct. They showed significant evolutionary change during their era and seemed capable of exploiting a range of ecological niches.

Crystals (UK) buys its ammonites from Madagascar, Morocco, Russia and Whitby, North Yorkshire. Our 'Open Me' ammonite pairs are generally prepared form North Yorkshire material by a fossil quarry owner's father.

Here at Crystals (UK) we have many, many stories to tell about ammonites. members of our team remember vividly the occasion of arriving in a Madagascan house in a tropical rainstorm. In low, or non-existent lighting conditions, while massive lightening flashed outside the window, we slowly realised the whole house was full of ammonites! The vendor's late husband had been a lifelong ammonite collector. We bought ammonites from very unusual locations that night including the bed linen drawer, all magnificently prepared, many with the stunning red flashes.