Magnetite

specimen number:
2102426

location:
Empire State No. 4 Mine, Balmat, Fowler, St. Lawrence Co., New York, USA

description:
Lustrous black sharp cubic crystals of magnetite to 1.3 cm on edge across matrix with minor anhydrite. Some contacting present, this natural, overall in good condition. From the early 1990s.

The Empire State No. 4 mine, situated in the Balmat-Edwards-Pierrepont zinc district within St. Lawrence County, New York, is a premier industrial underground zinc operation. Geologically, the deposit is a highly metamorphosed, stratabound zinc sulfide body hosted within Precambrian metasedimentary rocks of the Grenville Province, specifically localized within complexly folded silicated marbles and evaporite sequences. The primary ore mineral is sphalerite, which occurs in massive, high-grade tabular zones alongside pyrite, galena, and various calcium-magnesium silicate gangue minerals. The mineralized zone for the No. 4 shaft was originally discovered in 1965 through a systematic surface fence-drilling program across the Sylvia Lake Syncline. Underground development and commercial extraction began following shaft completion, with major expansions such as the Mud Pond and New Fold zones adding reserves throughout the 1990s. The facility was historically operated by companies like the St. Joseph Lead Company and the Zinc Corporation of America, and after brief periods of care and maintenance, it remains an active producer under modern corporate ownership.

In 1991, underground operations within the Fowler orebody of the mine encountered an altered area of highly unusual mineralization on the 2500-foot level, leading to a remarkable discovery of magnetite crystals. While magnetite typically forms octahedral crystals, this specific pocket yielded sharp, jet-black crystals dominated by the rare cubic form, modified by minor tetrahexahedral faces. These highly lustrous, three-dimensional specimens occurred either lining halite-filled veins or embedded within a soft matrix of halite and talc, accompanied by anhydrite, sphalerite, and calcite. The recovery of these blocky, near-perfect cubes throughout 1991 and 1992 created an immediate sensation in the mineralogical community because cubic morphology is exceptionally rare for this iron oxide species. These specimens remain benchmark examples for the locality, representing one of the most significant morphological oddities discovered in the region during the late twentieth century.

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