Iridescent ammonites and ammolite
Iridescent ammonites are reputed worldwide for their beautiful rainbow-like glow. A special gemstone, ammolite, is formed from fossilised ammonite shells, and also displays this terrific iridescent effect. When the ammonite was alive, nacre was the main component of the shell: after the organism’s death, the shell fossilised over time to form aragonite. The ammolite can also contain many other minerals such as calcite and pyrite. Ammolite is not only rare for its vibrant display of colours, but also for the fact that it is biogenic. Most gemstones are not produced by living creatures. However, ammolite (like amber and pearl, the only other biogenic gemstones in the world), is formed from living organisms: ammonites, one of the world’s most beloved fossilised creatures.
Ammolite is only found in very specific places, such as the Rocky Mountains of the USA. Hundreds of millions of years ago, ammonites of the species Placenticeras meeki and Placenticeras intercalare populated the Western Interior Seaway, bordering the Rocky Mountains: when they died, they were fossilized and their aragonite shells became what is now known as ammolite. This process also occurred nearby in the Bearpaw Formation connecting to Alberta, Canada. Korite is a mining company located in Alberta, and therefore is the largest supplier of ammolite in the world.
Within the aragonite shell of ammolite, thin platelets are present. When light is shone on an ammolite specimen, light is reflected from these platelet layers and interference occurs. This leads to the vivid spectrum of colour observed in ammolite, usually consisting of red and green hues. Thin platelet layers tend to result in blue and violet shades, whereas thick platelet layers often lead to an iridescent effect mostly consisting of the usual greens and reds. Similarly, labradorite is a gemstone which displays an iridescent effect referred to as ‘labradorescence’, or the Schiller effect.
In myth, the Native American Blackfeet tribe refer to ammolite as a ‘buffalo stone’ for its reputed qualities of helping to cause a successful buffalo hunt. They also ascribed medicinal powers to the gem, contributing to its rich legacy.
At Madagascan Direct, we do not sell ammolite, but we do sell equally beautiful iridescent ammonites; the shells of which form ammolite when the ammonites are from the Alberta area. Our iridescent ammonites, sourced from Madagascar, include Cleoniceras species displaying a dazzling opalescent effect. Found in the jungles of Mahajanga on the north west coast of Madagascar, these ‘fire ammonites’ are perfect display pieces for your home. Madagascan Direct’s catalogue also includes iridescent-ammonite based jewellery. Using ammonites from the cretaceous period, we sell iridescent ammonite cabochon pendants and rings, as well as iridescent ammonite pendants which retain their full iconic shape.