|Ammolite is an opal-like organic gemstone found mainly along the eastern slopes of the Rocky Mountains of North America. Alberta has produced the finest examples. It is composed primarily of aragonite, the same mineral that makes up nacreous pearls. |
It is one of the few biogenic gemstones; others include amber, pearl and coral.
|An iridescent opal-like play of colour is shown in fine examples, mostly in shades of green and red although all the spectral colors are possible. |
Iridescence is due to the microstructure of the aragonite: unlike most other gems, whose colors come from light absorption, the iridescent color of ammolite comes from interference with the light that rebounds from stacked layers of thin platelets that make up the aragonite.
|The thicker the layers, the more reds and greens are produced; the thinner the layers, the more blues and violets.|
Gem ammolite is rare and in strong demand among jewelry buyers and collectors world-wide.