Pyrolusite (MnO₂) is the most common manganese ore mineral and the principal source of industrial manganese for steelmaking and battery production. While massive forms dominate the ore market, collectors prize the dendritic “manganese trees” that grow along fracture surfaces in sedimentary rocks, and rare botryoidal or fibrous crystalline aggregates from oxidized manganese deposits.
Key Facts
- Mohs hardness varies dramatically: 2 for soft sooty masses, up to 6.5 for compact crystalline material.
- Tetragonal, isostructural with rutile.
- Black to dark steel-gray with metallic to dull luster.
- Famous for dendritic growths on bedding planes — often mistaken for plant fossils.
- Major ore at Postmasburg (S. Africa), Nikopol (Ukraine), and Hunan/Guangxi (China).
Notable Chinese Localities
Hunan and Guangxi host the largest Chinese manganese fields. Botryoidal and fibrous specimens are mined as byproducts of industrial Mn extraction.
