mineral

Ammolite

Biogenic gemstone (Aragonite, CaCO3)

Hardness: 3.5-4.5 (Mohs scale); Color: Iridescent play-of-color (red, green, blue, yellow); Luster: Vitreous to resinous; Structure: Orthorhombic (thin layers); Specific Gravity: 2.75-2.85

Hardness: 3
Color: Iridescent play-of-color (red, green, blue, yellow)
Luster: Vitreous to resinous

Identified March 30, 2026More mineral →

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Physical properties

Hardness: 3.5-4.5 (Mohs scale); Color: Iridescent play-of-color (red, green, blue, yellow); Luster: Vitreous to resinous; Structure: Orthorhombic (thin layers); Specific Gravity: 2.75-2.85

Formation & geological history

Formed from the fossilized shells of extinct ammonites (Placenticeras meeki and Placenticeras intercalare) during the Upper Cretaceous period (70-75 million years ago) in the Bearpaw Formation.

Uses & applications

Primarily used as a gemstone in high-end jewelry (cabochons), as decorative display specimens, and in Feng Shui practices.

Geological facts

Ammolite is one of the few biogenic gemstones (alongside pearls and amber) and was recognized as an official gemstone by the CIBJO only in 1981. It is often reinforced with a cap of synthetic spinel or quartz because it is very thin and fragile.

Field identification & locations

Identify by its 'dragon skin' pattern and intense rainbow iridization. It is found almost exclusively along the eastern slopes of the Canadian Rockies in Alberta, Canada. Collectors look for vibrant colors and a full spectrum of the rainbow.