Ammolite is a rare and valuable opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is arguably the rarest gemstone on earth, rivaling the rarity of such gemstones as alexandrite and red diamonds. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral that makes up nacreous pearls.
Ammolite
