Pyrolusite

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Lustrous black bladed crystals of pyrolusite measuring to 3.5 cm in length across the top of matrix. This is in good condition and excellent for the species, especially for this locality. Collected by Olive Sain.Pyrolusite is a manganese oxide mineral that commonly forms in the oxidized zones of manganese bearing deposits. It typically appears as dark gray to black fibrous or massive material and is an important ore of manganese. Specimens are well known for their quality at this locality, where small mining operations explored iron and manganese bearing deposits in Precambrian rocks of the Upper Peninsula. Although the region was known mainly for iron mining, secondary manganese minerals such as pyrolusite have been found in altered zones of the host rock.