MnO₂

These samples of pyrolusite are displayed in the Smithsonian Museum of Natural History. Pyrolusite is an oxide mineral of manganese with the composition MnO₂ . This sample of pyrolusite is about 14 cm across and is from Amapa Territory, Serra do Navio, Brazil.

This sample of pyrolusite is from Boston Hill Mine, Silver City , New Mexico. The sample is about 8x10 cm.

See manganese oxide for an example of dendritic crystal growth.

This sample is about 6x6 cm and is from Marienberg, Westerwald, Rhineland-Pfalz, Germany.