Cummingtonite with Rhodonite

specimen number:
2133288

location:
Morro da Mina, Conselheiro Lafaiete, Minas Gerais, Brazil

description:
Fibrous cummingtonite on matrix with rhodonite. A good example for the species.

The Morro da Mina mine, situated near Conselheiro Lafaiete within the upper Paraopeba River basin of Minas Gerais, Brazil, is a historic and massive industrial open-cast manganese operation recognized by mineral collectors for yielding highly distinct, localized specimens of the magnesium-iron amphibole cummingtonite closely associated with rich pinkish-red masses and crystalline groups of rhodonite. Geologically, this major deposit is located within the Paleoproterozoic-age Barbacena Greenstone Belt, where extensive primary marine manganiferous carbonate and silicate sediments underwent high-grade regional metamorphism exceeding 600 degrees Celsius to form a unique, localized manganese-rich rock suite known as queluzite. Intense metamorphic recrystallization and subsequent late-stage shearing concentrated specific chemical ions within localized fracture zones, allowing pale greenish-to-brownish fibrous aggregates of cummingtonite to form directly alongside deep cherry-red, highly saturated rhodonite, pyroxmangite, and spessartine garnet. Historically, large-scale open-pit quarrying and mechanized extraction at Morro da Mina officially commenced in 1902, with the site quickly establishing itself as the premier manganese producer in Brazil and later undergoing decades of intensive development under corporate operators like United States Steel to supply essential metallurgical-grade ores to global markets.

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