Calcite

specimen number:
1631186

location:
CRD, Sweetwater mine, Reynolds Co., Missouri, USA

description:
From fairly recent collecting in the Cemetery Ridge development area, a grouping of lustrous golden scalenohedral calcite crystals without matrix. Some damage and cleaving present as seen, the prominent crystal terminations are in good condition and show high transparency.

The Sweetwater Mine, located in Reynolds County, Missouri, is a major component of the world-class Viburnum Trend, which is the most productive lead-mining district in history. Geologically, it is a classic Mississippi Valley-Type (MVT) deposit, where mineral-rich brines migrated through porous sedimentary rocks during the Appalachian-Ouachita orogenies. The mineralization is primarily hosted within the Cambrian-aged Bonneterre Formation, a massive dolostone rock that provided the chemical environment necessary to precipitate sulfides like galena, sphalerite, and chalcopyrite. Historically, the mine began operations in the late 1960s under the Ozark Lead Company and was later acquired by the Doe Run Company. While its primary industrial purpose is the extraction of lead and zinc, the mine is globally famous for the massive hydrothermal vugs and solution cavities discovered during the mining process, which are often lined with spectacular, well-crystallized secondary minerals.

For mineral collectors, the Sweetwater Mine is most iconic for its world-class calcite specimens, which are considered some of the finest examples of the species. These calcites typically form as sharp, doubly terminated rhombohedrons or complex scalenohedrons; while many are smaller, individual crystals can rarely reach massive sizes of 60 cm or more. They are celebrated for their distinctive honey-yellow to amber color and their translucent to opaque clarity, frequently exhibiting a glassy luster. A hallmark of Sweetwater calcite is its aesthetic association with a dark matrix of metallic minerals like galena or brassy chalcopyrite, often sitting upon a base of the host dolostone. These specimens are highly prized for their architectural beauty and the way they represent the final, low-temperature stage of the mineralization process in the Ozark Plateau. Because of their potential for enormous size and geometric perfection, they are centerpiece items in major museum collections and remain a gold standard for Missouri mineralogy.

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