Ramsdellite

specimen number:
2102275

location:
Mistake Mine, Yavapai Co., Arizona, USA

description:
Blocky somewhat lustrous crystals of ramsdellite measuring to 0.5 cm in size on matrix. Good example for the species.

The Mistake Mine, located in the Sam Powell district of Yavapai County, Arizona, is a notable locality for manganese oxides situated within the rugged Basin and Range province. Geologically, the deposit occurs as hydrothermal vein and replacement mineralization within Tertiary-aged volcanic and sedimentary rocks, where manganese-rich fluids precipitated various oxide species in open cavities and fractures. The site is mineralogically significant for producing exceptional crystals of ramsdellite, a rare manganese dioxide polymorph, which typically appears as lustrous, metallic-gray to black orthorhombic prisms or radiating aggregates. Historically, the mine was active primarily during the mid-20th century, with significant production occurring between the 1950s and early 1960s to meet the demand for strategic minerals during the Cold War era. While the operation was relatively small compared to Arizona's massive copper pits, the quality of its crystallized manganese specimens has made it a well-known name among mineral collectors and researchers studying the oxidation of manganese deposits in arid environments.

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