Pyrolusite is tetragonal and ramsdellite is orthorhombic. A third mineral, akhtenskite , is much more rare than these two and is also a polymorph being hexagonal. The three minerals are thus referred to as trimorphs. Ramsdellite is an oxidation product of weathered manganese minerals, such as manganite . Manganese is a strategically valuable metal since it is an essential ingredient in steel and other alloys.
Color is black to gray.
Luster is metallic to dull. Crystals are opaque, translucent in only thin splinters. Crystal Habit is typically massive and granular. Crystals are uncommon and tabular. Cleavage is good , but rarely seen except in rare large crystals.