Magnetite

specimen number:
2102371

location:
ZCA West Pierrepont Mine, St. Lawrence Co., New York, USA

description:

Bright lustrous sharp cubic crystals of magnetite measuring to 1.4 cm on edge across the top of matrix. In good condition with minimal damage present. This is from the early 1990s and represents and neat find for the species.

The Zinc Corporation of America Mine Number 4, situated within the Balmat-Edwards mining district in St. Lawrence County, New York, was a world-class underground zinc operation that achieved international mineralogical fame in the early 1990s for producing some of the world's finest sharp, cubic magnetite crystals. Geologically, the Balmat deposit is located within the highly metamorphosed Proterozoic-age Grenville Province and consists of massive, stratabound, volcanogenic sedimentary exhalative (SEDEX) zinc sulfide bodies hosted within highly deformed silicated marbles and calc-silicate rocks. In 1992, miners advancing underground workings on the 2500-foot level broke into a remarkable, fluid-filled solution cavity within the dolomitic marble that contained incredibly sharp, lustrous, modified cubic crystals of magnetite measuring up to several centimeters across, striking mineralogical anomalies given that magnetite typically crystallizes in octahedral forms. Historically, corporate mining in the district began in earnest during the late 1920s under the St. Joseph Lead Company, with the specialized Mine Number 4 shaft being sunk in the 1960s to access deep ore zones before ownership transitioned to the Zinc Corporation of America (ZCA) in 1987. Regular commercial underground extraction and on-site milling at Mine Number 4 operated continuously until a severe zinc market downturn forced a full suspension of corporate operations in 2001, though the deep shaft infrastructure was later integrated into subsequent corporate redevelopment and modern re-opening cycles that continue under current management through 2026.

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