Polianite

Polianite is a mineral species of manganese oxide. Its chemical formula is MnO2, with minor amounts of iron and other elements present. Polianite is the highest temperature polymorph of manganese dioxide. It crystallizes in the tetragonal crystal system. The mineral typically appears as dark gray to black prismatic or acicular crystals. It can also occur as massive or granular aggregates. Polianite is relatively hard, with a Mohs hardness of 6 to 6.5. Its specific gravity is around 4.8 to 5.0. It is insoluble in common acids. Polianite is often found in hydrothermal veins and metamorphic rocks, particularly those that have undergone high-temperature alteration. It is also found in some oxidized manganese deposits. Associated minerals may include other manganese oxides, quartz, calcite, and rhodonite. Polianite is named after the Russian mineralogist A. I. Polyan. While it is a manganese ore, it is generally not as economically significant as pyrolusite, which is another polymorph of MnO2. The distinction between polianite and pyrolusite can sometimes be challenging without detailed crystallographic analysis.