CANADIAN AMMONITE - AMMOLITE

“Ammolite” is the name given to the colorful and wonderful ammonite fossils found in Southern Alberta. It is an opal-like gem mineral that displays an extraordinary play of color ranging from bright red all the way to deep violets. Their shells underwent a unique fossilization process from exposure to pressure, temperature and geographic location which caused the animal’s shell to recrystallize into amazing iridescent colors.

These unique treasures can only be found in one location worldwide - in the famous Bear Paw Formation in the southwest of Alberta, Canada. The specimens are mined on the Native American Blackfoot reservation, who themselves operate and oversee the excavation and production.

Since 1981 it is recognized as a gemstone by the CIBJO Colored Stones Commission. Ammolite is the only material in the world considered to be Fossil, Mineral and Gemstone.

The Bearpaw Formation is exposed at Earth's surface in parts of Alberta, Saskatchewan, Montana, and Utah. The only area known to yield gem-quality Ammolite in commercial amounts is located along the St. Mary River in southwestern Alberta, but small amounts of gem Ammolite have been found in other areas.

Multiple layers of hard siderite concretions can be found within the Bearpaw formation, this is where you usually find Ammolite specimens since these concretions generally form around a nucleus which is commonly a fossil. The shape of these concretions generally closely resembles the fossil contained within. This makes finding ammolite-bearing concretions easier as they are typically more disk-shaped than other concretions surrounding them. The size of the disk-shaped concretions also is a good indication of the size of the specimen held within.
Over time the minerals, namely Siderite, in these concretions formed a thin neatly stacked layers of Calcium Carbonate platelets known as Aragonite. These aragonite platelet layers cause light interference between them and are the cause of Ammolite’s amazing play of color. This is very similar to that of opal, which also owes its color due to light interference and absorption. The main difference however is that in opal the play of color is also caused by diffraction and interference but instead of layers, the opal is made up of sub-microscopic spheres which are regularly stacked with spaces of only a few hundred nanometers between them. The resulting colors depend on the size and structure of the spheres.
The origin of ammolite dates back about 70 to 75 million years ago when a number of smaller tectonic plates began sliding under the North American plate which caused the formation of the northern part of the Rocky mountains in what is now the northwestern part of North America.

With the Western interior seaway to the east of the mountains, rain started washing shale sediments into the seaway and over time formed the Bearpaw formation.
The western interior seaway was host to a large array of marine fauna, with one of the more odd-looking creatures being the “ammonite”. Ammonites were squid-like creatures with a coiled shell. When these creatures died and reached the sea floor their shells were covered by shale sediment, forming concretions around them.
The size of Alberta's Ammolite resource is difficult to assess. Searching outcrops does not yield reliable information because weathering has destroyed and altered much of the original Ammolite. The productive zones in the Bearpaw Formation are only a few feet thick, and the gem material is concentrated in large fossils. This makes drilling an ineffective exploration method.Iridescent ammonite fossils are found in many outcrops of the Bearpaw Formation, but these are often too damaged by weathering to serve as good gem materials, let alone complete specimens. The best gem-quality material is found in the excavations of mining operations where depth has protected the Ammolite from weathering. Some of it still requires stabilization to be used as a gem material. Some of it is too thin for use in manufacturing.In areas where there is a potential for gem-quality material, the Bearpaw Formation is typically dipping. This limits mining to a thin zone between the outcrop and where the overburden is too thick to mine profitably. This limits the size and value of any discovery. Together, these facts make Ammolite a uniquely rare material.
Once prospecting pays off and miners discover a concretion that contains gem-quality ammolite the specimen is carefully moved to a site for processing where the matrix surrounding the ammolite is meticulously removed being very careful not to damage the thin layer of ammolite it surrounds. Once one side of the ammolite is uncovered it is inspected, paying close attention to the stability of the piece and whether it is safe enough to start removing the matrix on the other side. This may not always be the case since the fossils themselves have been subjected to large amounts of pressure when they got covered in sediment and are very often broken and compressed. This makes it exceedingly rare to find a completely intact ammolite fossil. Preparators always hope to uncover a specimen that is complete on both sides and displays the entire color spectrum.
Interprospekt is a company that prides itself on ethical and sustainable mining practices around the world and partnering up with local people to enrich the local communities. Interprospekt as a company has over many years built up a very good relationship with the blackfoot natives that own the land and mineral rights to a large part of the Bearpaw formation. This relationship eventually lead to a fairtrade agreement being set up between them, making interprospekt the premier source of world-class ammolite specimens.
Click here to read the full article 'Ammolite - Ancient Origins of a modern Opal-Like Marvel by our gemmologist Andor Koot

HISTORY

Ammolite may be a relatively new material to the mineral industry, but the blackfoot natives have a long history with the material dating back hundreds of years. They called the material “Iniskim” which translates to buffalo stone in their native tongue and used it as a talisman.

The first scientific accounts on the colorful ammonite shells now known as “Ammolite” were done back in 1908 by scientists from the Canadian Geological Survey. Due to Ammolite’s rarity however it wasn’t until the 60s that material first started appearing at gem and mineral shows.

Marcel Charbonneau, owner of a Calgary rock shop, saw the potential in this material and began assembling doublets of iridescent ammonite shell on matrix with a clear quartz cap, renaming them "Ammolite". The material quickly became popular. In 1981, Ammolite was recognized as a gemstone by CIBJO Colored Stones Commission, and in 2004 it was named as the official gemstone of the Province of Alberta. The Colored Stones Commission brought international attention to Ammolite and it becoming the official Alberta gemstone produced enormous local popularity.

The size of Alberta's Ammolite resource is difficult to assess. Searching outcrops does not yield reliable information because weathering has destroyed and altered much of the original Ammolite. The productive zones in the Bearpaw Formation are only a few feet thick, and the gem material is concentrated in large fossils. This makes drilling an ineffective exploration method.

Iridescent ammonite fossils are found in many outcrops of the Bearpaw Formation, but these are often too damaged by weathering to serve as good gem materials, let alone complete specimens. The best gem-quality material is found in the excavations of mining operations where depth has protected the Ammolite from weathering. Some of it still requires stabilization to be used as a gem material. Some of it is too thin for use in manufacturing.

In areas where there is a potential for gem-quality material, the Bearpaw Formation is typically dipping. This limits mining to a thin zone between the outcrop and where the overburden is too thick to mine profitably. This limits the size and value of any discovery. Together, these facts make Ammolite a uniquely rare material.

AMMOLITE

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CANADIAN AMMONITE - AMMOLITE

AN INTRODUCTION TO AMMOLITE

HISTORY

AMMOLITE