New Mexico Mineral Symposium — Abstracts

Well-formed crystals of magnetite have been found in the Republic pit and several other mines in the Hanover¬Fierro district of Grant County, New Mexico. The crystals occur in skarns along the margin of a Tertiary granodiorite porphyry intrusive where it invaded Silurian and Ordovician dolomite. Although massive magnetite is common, the skarns occasionally contain areas with well-formed magnetite crystals that have grown in coarse crystalline calcite. The crystals usually occur as simple, sharp, equant octahedrons and can be as large as 3 or 4 inches on edge. Fine specimens have been obtained by dissolving the calcite from chunks of the magnetite-calcite skarn displaying sharp crystal outlines.

The Republic pit is a part of a group of mines operated by the Hanover Bessemer Iron Ore Association in 1894. Other properties included the Union Hill, the Anson S., and the Jim Fair pit. The mines were worked by a variety of owners over the years until 1931 when they closed for good. The property then passed through several hands and is now owned by Cobre Mining Company, a subsidiary of Phelps Dodge Mining Company. In 1997 the Republic pit was covered with a waste stockpile and collecting opportunities ceased. Other deposits in the area contain similar mineralization although in lesser quantities.