page_title: Crowsnest Formation
section_title: Lithology and mineralogy
hierarchical_section_title: Crowsnest Formation / Lithology and mineralogy
caption_attribution_description: English: A specimen of blairmorite from the Crowsnest Formation in Alberta. Courtesy of C.W. Langenberg and Alberta Geological Survey.
context_page_description: The Crowsnest Formation, also called the Crowsnest Volcanics, is a geological formation in southwestern Alberta, Canada, on the southwestern margin of the Western Canada Sedimentary Basin. It was named for the Crowsnest Pass near Coleman, Alberta. The formation consists mostly of pyroclastic rocks that were laid down in a series of explosive eruptions about 100 million years ago during the Albian stage of the Early Cretaceous epoch. It contains unusual minerals such as melanite and analcime.
context_section_description: The formation contains pyroclastic flows, lahars, agglomerates, tuffs and ash-fall deposits, as well as volcanic-rich sandstones and other sediments. The whole-rock chemistry of the volcanics is relatively normal, ranging from trachyandesite (latite) to phonolite and trachyte, but the mineralogy is unusual. In addition to analcime and melanite, common minerals include sanidine, aegerine-augite and chlorite. Blairmorite, a rare analcime-rich rock-type named for the town of Blairmore, Alberta, is known only from the Crowsnest Formation and a locality in Mozambique.
caption: Blairmorite from the Crowsnest Formation. The amber mineral is analcime, the pale mineral is sanidine, and the small black minerals are melanite garnet. The specimen is about 17 cm (6.7 in) in length. Photo by P. Glombick, courtesy of Alberta Geological Survey.
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