Ramsdellite from the Mistake
Mine, AZ
CHEMISTRY - MnO2
CRYSTALLOGRAPHY - Orthorhombic
CRYSTAL GROWTH AND HABITS - Ramsdellite crystals are commonly pseudomorphs after Groutite. Ramsdellite is platy to fibrous and massive.
COLOR AND OPTICAL PROPERTIES - Steel gray to black with a slight yellowish tint.
HARDNESS - ~3
SPECIFIC GRAVITY - 4.6 - 4.8
LUSTER - Metallic black
STREAK - Black
BREAKABILITY - Cleavage for crystals is prominent; brittle.
OCCURRENCE - Ramsdellite forms as a secondary mineral in manganese deposits.
ASSOCIATED MINERALS - Pyrolusite, Hollandite
MINERAL NAME - Named after L. S. Ramsdell an American Mineralogist.