Jewelry Type - Ring  Product Weight (gram) - 7.81 (approx) Stone - Ammolite Stone Size - 15 x 20 mm (approx) Metal - 925 Sterling Silver Metal Stamp - SJ925 The Ammonites which create Ammolite once inhabited an inland sea between 65 and 100 million years ago. As the seas gradually receded, the Ammonites were covered in layers of bentonite clay. This sedimental clay preserved the shells of the Ammonites, inhibiting their conversion into calcite. Whilst Ammonites are found all over the world, Ammolites are only found in the Rocky Mountains of North America.