Ammolite

Ammolite is a rare organic gemstone made from the fossilized shells of extinct ammonites, prized for its iridescent, multicoloured appearance.

Ammolite is a rare organic gemstone made from the fossilized shells of extinct ammonites, prized for its iridescent, multicoloured appearance. Commercial gem-quality ammolite is found primarily in southern Alberta, Canada, within the Bearpaw Formation along the eastern slopes of the Rocky Mountains. It is considered one of the rarest gemstones because gem-quality material is geographically limited.

Origin and formation

Ammolite forms from the fossilized shells of ancient ammonites, marine cephalopods that lived in the Western Interior Seaway. The shell material is mainly aragonite, and preserved nacre-like layers produce the gemstone’s characteristic iridescence.

Occurrence and mining

Commercial ammolite is sourced almost entirely from southern Alberta, especially near the St. Mary River and Bearpaw Formation deposits. The material is typically recovered through mining and natural erosion.

Appearance and gem use

Ammolite is valued for its vivid colour play, which can range across much of the visible spectrum or appear in limited colour bands. It is typically fashioned into cabochons and assembled jewellery because gem-quality layers are often thin and fragile.

Status and significance

Ammolite is one of the few biogenic gemstones, alongside amber and pearl. It has been officially recognized by the World Jewellery Confederation and is associated with Alberta’s gemstone identity.