Friedelite - Encyclopedia
Class : Silicates
Subclass : Sorosilicates
Crystal system : Monoclinic
Chemistry : Mn8Si6O15(OH,Cl)10
Rarity : Quite common
Friedelite is a phyllosilicate which forms at the expense of manganese silicates in areas having undergone contact metamorphism ; it is associated with rhodochrosite, rhodonite and generally with manganese minerals. It is the dimorph of pyrosmalite, with hexagonal symmetry. Its name was given to it in honor of the French chemist and mineralogist Charles Friedel. Friedelite forms typical pseudohexagonal, tabular crystals, frequently hemimorphic, more rarely fibrous or acicular crystals ; it also forms cryptocrystalline or granular masses with a stalactitic appearance. Its color varies : pale pink to brownish red and dark brown, sometimes brownish yellow.
Main photo : Friedelite de N'Chwaning II Mine, South Africa © Bruce Cairncross
Friedelite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 4 to 5
Density : 3.05
Fracture : Sub-conchoidal
Streak : White
TP : Translucent to transparent
RI : 1.625 to 1.656
Birefringence : 0.032
Optical character : Biaxial
Pleochroism : None
Fluorescence : None
Solubility : Hydrochloric acid
Magnetism : None
Radioactivity : None