Ammolite is an opal-like organic gemstone found primarily in the Rocky Mountains of North America. It is made of the fossilized shells of ammonites (extinct marine mollusks). Why they look like Ammolite: Iridescence: The vibrant, "electric" green color that seems to shift with the light is a classic hallmark of this stone. Fracture Pattern: If you look closely at the top earring, you can see fine, stained-glass-like lines. This is often called a "dragon skin" or "stained glass" pattern, which occurs naturally as the fossilized shell is compressed over millions of years.