Long ago, around 100 million years ago, the Western Interior Seaway stretched to the east of the Rocky Mountains on the American continent. Where taiga and prairies now extend, salty sea waves were once driven by the wind, and the depths beneath them teemed with ancient life. Schools of fish hunted cephalopods known as belemnites. Larger fish, including ancient sharks, competed with six-meter-long Xiphactinus for prey. But even these predators met their demise in the jaws of pliosaurs, enormous marine reptiles. The era of reptiles was nearing its end, but for now, pliosaurs with short necks and powerful jaws, graceful long-necked elasmosaurs, and various marine crocodiles enjoyed their dominance in the seas. In this dangerous world lived our heroes—the ammonites. These cephalopods with spiral shells hunted small fish in the water column, diving and ascending like miniature submarines. When death found them, either from a pliosaur’s teeth or a large fish, the mollusk’s shell sank to the seabed, quickly covered by sand and silt due to strong bottom currents. Gradually, over tens of thousands of years, some of these shells fossilized. Rivers flowing into this shallow sea from the Rocky Mountains enriched the waters with salts and minerals, creating a unique chemical environment. In these conditions, the mollusk’s shell decayed slowly, allowing the inner nacreous layer to become infused with iron and silicon compounds, preserving it for millions of years.

Ammolite, according to geological classification, is a gemstone that is not a mineral but consists of fossilized fragments of the nacreous layer of ammonite shells. Although the stone has been known for a long time, it was recognized as a gemstone only in 1981, which marked the beginning of its commercial extraction. In 2004, ammolite was named the official gemstone of the Canadian province of Alberta. The name “ammolite” is derived from two words: “ammo-” from “ammonite,” and “lithos,” meaning stone.

Typically, the internet mentions the “Bearpaw” formation in Canada, a certain St. Mary River in an unspecified location, the “Kainah Indian Reserve,” and the Ulyanovsk region in Russia. It is often emphasized that ammolite exists only in Canada. Let’s clarify.

In small quantities, mollusk shells with preserved nacreous layers are found all over the world. However, they typically resemble regular nacre, lacking the iridescent glow and color diversity characteristic of ammolite. Iridescence (the rainbow-like glow with a 3D effect) in ammonite shells is much rarer but does occur. However, it is only in Canada, in the province of Alberta, where the unique conditions that transformed this iridescent nacreous layer into a gemstone converged. The name “ammolite” is specifically associated with these Canadian treasures.

The Bearpaw formation is a geological layer that extends in a narrow strip along the eastern edge of the Rocky Mountains, from Alberta, Canada, to Utah, USA. The layer lies at a depth of 15 meters and has a thickness of another 15 meters. In Canada, the Kainah Indian Reserve is also located in this region, through which the St. Mary River flows. And what about the Ulyanovsk region? Yes, it boasts fantastic specimens with beautiful nacreous layers that can rival Canadian ammolite in beauty. But still, it is not ammolite.

Mining is conducted via open-pit methods, and mining companies reclaim the landscape after extraction (even restoring local vegetation). However, fortune may also smile on private treasure hunters. Downstream of the St. Mary River, one can find worthy specimens washed out by the river’s waters from its banks. What kind of luck could such a find bring? Well, the price of a large, high-quality ammolite at jewelry auctions can reach up to $200,000.

Ammolite reserves are not infinite, and they may be depleted for commercial mining in as little as 20 years. However, individual specimens will likely continue to be found, delighting gem hunters for a long time.

Ammolite has a complex chemical composition. The primary substance it consists of is calcium carbonate, CaCO₃. There are several stable forms of calcium carbonate, and in mollusk shells, this is aragonite. Flat hexagonal plates of aragonite crystals layer upon each other, forming the nacre that lines the inner layer of the shell.

During fossilization, some of the aragonite is replaced by compounds of other substances, primarily pyrite (FeS₂) and quartz (SiO₂), which form significant impurities. Additionally, aluminum, barium, copper, manganese, strontium, titanium, vanadium, and other elements are present.

How is the iridescent (rainbow) effect formed? The multilayered microstructure of nacre refracts light, creating an interference effect. White light is split into its color components and scattered in all directions. As a result, the viewer sees different colors from different angles, resembling the rainbow film on the surface of a soap bubble or the similar glow of opal. In “fresh” nacre, the effect is weak due to protein layers between the aragonite crystal layers. In ammolite, however, the organic material has been replaced by quartz and pyrite, creating an entirely fantastic visual display.

The primary colors of ammolite are combinations of red and green with yellow, orange, blue-green, and blue. These colors are produced by thicker and stronger layers of aragonite. Ammolites with purple and pink hues are rarer, as these colors require more fragile aragonite layers.

Freshly mined ammolite usually doesn’t show much color and appears rather dull. To reveal its full color palette, it requires processing. Sometimes, it starts to shine after quality polishing, but typically, the processing is much more complex.

Ammolite is generally a fragile and sensitive stone. It has a layered structure and can be easily scratched with a knife. To strengthen it, it is often impregnated with special polymers or epoxy resin.

It’s also important to remember that this is the inner layer of a shell, meaning it is often hidden beneath layers of fossilized ammonite shell remains. Removing these layers and revealing the stone’s beauty requires a true master, and needless to say, the work is done by hand. As the layers of aragonite are removed, the master aims to uncover all the colors within the stone. Such stones, containing the full rainbow palette, are the most highly valued. Another approach to processing is to highlight shades of a single color; this method is usually applied to stones with purple and pink hues.

The result is a beautiful, unique work of art. In the play of colors and shades, people see stunning images, reminiscent of a starry sky, the intertwining arms of galaxies, and cosmic nebulae.

Because processing ammolite is challenging, large ammolites with their host rock are not used in jewelry—they are considered collectible specimens. For creating jewelry, only the nacreous fragments of ammolite are used.

The ammonite shell is cut into the thinnest layers using a laser, separating a thin layer of ancient nacre. This is then adhered to a base of synthetic black spinel and may be further coated with a layer of quartz for added strength. Light passing through the nacre layer reflects off the spinel matrix, enhancing the natural effect of iridescent glow and the stone’s “depth.”

Despite the complexity of the technology, such ammolite composites are valued much less than whole stones. They are used to make brooches, earrings, pendants, and other jewelry. Ammolite jewelry requires careful handling; it should be stored wrapped in special fabric in jewelry boxes. For cleaning, a mild soap solution is used, in which the stone is immersed for 20-30 minutes, then rinsed under running water and wiped with a soft cloth.

Ammolite has been known to the indigenous people of the Rocky Mountains and adjacent prairies for ages. In the Blackfoot language, it is called “aapoak,” meaning “small crawling/serpent stone.” It is said to have been used as a talisman during bison hunts. Figures of bison were carved from it, which were believed to bring luck, health, and strength to the owner.

In modern esotericism, the stone has only recently gained recognition, and its symbolism is strongly associated with the water element, which is explained by its origin. The stone is recommended for sailors and divers, as well as for anyone connected to the sea or having another “watery” profession. The spiral shape of large ammolites is also subject to esoteric interpretation. The spiral is a symbol of order and creation, meaning that the life of the stone’s owner will become structured, and their thoughts more logical and rational.