Ammolite is an iridescent gemstone which originates primarily in the Rocky Mountains of North America, although limited deposits can also be found in other regions of the world. This gemstone is also referred to as korite, aapoak, calcenite, or gem ammonite. This gemstone has been used in jewelry since the late 1960s, and was officially granted status as a gemstone in the 1980s, making it one of the more recent gems on the market.
Although ammolite wasn't recognized as a gemstone until the 20th century, the origins of this gemstone are ancient. It is made from the mineralized remains of ammonites, sea creatures which became extinct millions of years ago. In the right conditions, the shells of ammonites were covered in layers of sediment, and a very slow process of mineral deposition fossilized the shells, turning them into ammolite. Around half of the ammolite recovered in mining operations is considered “gem grade,” with most coming from Canada.
The iridescent appearance of this gem is created by the refraction of light as it passes through the layers in the fossil. The layers are extremely thin and prone to cracking and flaking, but they can produce a range of colors including blue, violet, green, red, and pink. Red to green patterns are most common. Since this material is so fragile, it is usually sold with a supportive backing, which may consist of the stone the ammolite was found in, or of a replacement backing such as shale or even glass.
Ammolite is often sold in the form of triplets, stones which include a backing, the ammolite itself, and a protective crystal cap. It is around a four on the Mohs Scale, and triplets have an increased hardness of seven to eight, making them much sturdier. Care must still be taken to avoid exposing pieces to harsh chemicals and excessive sunlight, as the stone is prone to fading and flaking even with a protective cap.
The opalescent look of this material leads many people to compare it to opal or mother of pearl, and in fact the primary mineral present in ammolite is the same mineral which gives mother of pearl its luminescent glow. Most classically, it is sold in the form of polished cabochons which are used in necklaces, earrings, and brooches. Rings made from this mineral must be carefully designed to protect the stone, as rings are subject to more trauma than other jewelry.