CORONADITE
Class : Oxides and hydroxides
Subclass : Oxides
Crystal system : Monoclinic
Chemistry : PbMn8O16
Rarity : Uncommon
Coronadite is an oxide of manganese and lead, sometimes slightly hydrated, frequently showing low iron and aluminum contents. It is a secondary mineral which forms in the upper oxidized part of lead and manganese deposits, perhaps by recrystallization of a lead-bearing psilomelane. It takes its name from its place of discovery : the Coronado vein (Arizona, USA). It is usually massive, constituting botryoidal or nipple-like masses with a fibrous or fibrolamellar texture, with a surface commonly bristling with small crystalline points. Its color is light gray to black, with a semi-metallic to dull luster ; it is distinguished from other manganese oxides by its high density (nearly 5). It is occasionally an ore of manganese and lead.
Main photo : Coronadite from Rosh Pinah Mine, Ilkaras Region, Namibia © Bruce Cairncross
Coronadite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fake identified for this mineral species but can be difficult to differentiate from the psilomelane with which it shares its deposits.
Hardness : 4.5 to 5
Density : 5.24 to 5.50
Fracture : Irregular to fibrous
Streak : Brown-black
TP : Opaque
RI : -
Birefringence : -
Optical character : Biaxial
Pleochroism : None
Fluorescence : None
Solubility : -
Magnetism : None
Radioactivity : None