Goethite with Psilomelane

specimen number:
2062030

location:
Montreal Mine, Iron Co., Wisconsin, USA

description:
Fine botryoidal goethite and psilomelane mixed without matrix. This is in excellent condition and quite good for this famous old locality. At one time the specimen was part of the collection of Gene LaBerge.

The Montreal Mine in Iron County, Wisconsin was part of the Gogebic Iron Range along the Wisconsin Michigan border, one of the major iron producing regions in the United States. Mining began in the late 19th century to extract hematite ore from Precambrian banded iron formation. Underground operations supplied iron ore for the growing steel industry around the Great Lakes. Production continued for many years before the mine eventually closed in 1963 as high grade ore deposits were depleted.

Psilomelane is an old mineral name historically used for hard black manganese oxide material that commonly forms botryoidal or massive crusts in manganese deposits. It was once treated as a distinct mineral species, but modern mineralogy has shown that most material called psilomelane is actually a mixture of manganese oxides, commonly dominated by the mineral romanechite. These minerals form in the oxidized zones of manganese rich deposits and are often associated with other manganese minerals such as pyrolusite and manganite. The name psilomelane is still widely used by collectors to describe this type of botryoidal manganese oxide material.

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