Ammolite is approximately 70 millions years old and is formed from a rare, mineralized
fossil called an ammonite. Ammonites looked like giant Chambered Nautilus shells.
Ammolite has been formed by the compression and alteration of ammonite shell. Only
two species of ammonite produce gem material: Placenticeras meeki and intercalare.
These ammonites are found in the Bearpaw Formation (Upper Cretaceous) which extends
over a large part of Alberta into Montana, Wyoming, and the Dakotas. Gem quality
material is only found in the area between the Red Deer River and the Milk River in
southern Alberta. Ammolite is a multicolour opaque gemstone which resembles "boulder
opals". Gem quality ammolite is a crushed sheet of ammonite shell preserved in the
centre of ironstone concretions.

Ammolite comes from the fossil shells of the Upper Cretaceous disk-shaped ammonites
Placenticeras meeki and Placenticeras intercalare, and (to a lesser degree) the
cylindrical baculite Baculites compressus. Ammonites were cephalopods, or squid-like
creatures, that thrived in tropical seas until becoming extinct along with the dinosaurs
at the end of the Mesozoic era.

The ammonites that form ammolite inhabited a prehistoric, inland subtropical sea that
bordered the Rocky Mountains-this area is known today as the Cretaceous or Western
Interior Seaway. As the seas receded, the ammonites were buried and crushed by
layers of bentonite sediment. This sediment preserved the aragonite of their shelled
remains, preventing it from converting to calcite. Through diagenesis, the shells were
impregnated by trace elements present in these sediments, the most common of these
being iron and magnesium, the former of which accounts for the predominance of the
green colors.
In the late 1990s, practitioners of Feng Shui began to promote ammolite as an
"influential" stone with what they believe is the power to enhance well-being and
detoxify the body by improving its flow of energy or "chi". Named the "Seven Color
Prosperity Stone", each color is believed by Feng Shui practitioners to influence the
wearer in different and positive ways; a combination of ruby red, emerald green, and
amber yellow is most sought after for this purpose, the colors being said to enhance
growth, wisdom, and wealth, respectively.