Genesis of fibrous calcite and emerald by amagmatic processes in the southwestern Uinta Mountains, Utah

摘要

Large bodies of fibrous calcite, up to 400 m long and up to 20 m wide, are hosted by Mississippian carbonate units in the Uinta Mountains, Utah. Subjacent to the carbonate rocks, emerald mineralization has been recognized recently in the Neoproterozoic Red Pine Shale. Two types of fibrous calcites are recognized on the basis of appearance and geochemical characteristics. Fibrous orange calcite is translucent, similar to "Mexican calcite" commonly sold at gem-and-mineral shows, and is being mined and used in carvings and for other decorative purposes. Recently recognized fibrous brown calcite is also present in the same general vicinity.