Columbite - Etta Mine, Keystone, South Dakota, USA

Fe²⁺Nb₂O₆

The Etta Mine, located near Keystone, South Dakota, is renowned for its deposits of columbite, a niobium-tantalum oxide mineral that occurs in coarse-grained granite pegmatites. Columbite from the Etta Mine typically appears as dark black to brownish crystals with a submetallic luster, often embedded within the pegmatite matrix. These crystals can range in size, with some specimens being notably large and well-formed, making them highly prized by collectors. The mineral is often found in association with other pegmatite minerals such as spodumene, beryl, and cassiterite, reflecting the diverse and complex mineralogy of the Etta Mine’s geological environment.

Historically, the Etta Mine was an important source of niobium and tantalum, both of which are derived from columbite and are essential for industrial applications, including the production of high-strength alloys, electronics, and aerospace components. The mine’s deposits were extensively worked during the 20th century, contributing significantly to the strategic mineral supply of the United States. Today, columbite specimens from the Etta Mine are valued not only for their industrial relevance but also for their role in advancing the understanding of pegmatite formation and evolution. The Etta Mine stands as a classic locality in American mineralogy, showcasing the interplay between economic geology and scientific exploration.

Approx. specimen size: 65mm x 40mm x 17mm

Approx. specimen activity: 150 cpm