Glauconite - Encyclopedia
Class : Silicates
Subclass : Phyllosilicates
Crystal system : Monoclinic
Chemistry : (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2
Rarity : Common
Glauconite is a mineral close to the micas group to which it is sometimes attached, but its precise definition is complex and poorly defined. Some authors consider it to be a variety of celadonite. It is a biotite alteration mineral that forms in shallow marine environments under reducing conditions. Its name comes from the Greek glaukos (green-blue) because of its color. Glauconite occurs in small flattened pseudohexagonal crystals, yellowish green to blue-green in color, resembling chlorite, stacked on top of each other to form small, finely grained rounded clusters. Thanks to its high potassium content (4 to 9.5% K2O), glauconite is used in agriculture for soil amendment. It also has little use in the field of green pigments, and once played a role as an ion exchanger.
Main photo : Glauconite from the alluvium of the Loire, France © François Périnet
Glauconite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 2
Density : Underterminated
Fracture : Micaceous
Streak : Green
TP : Translucent to opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None
Solubility : Insoluble
Magnetism : Paramagnetic
Radioactivity : None