Beidellite - Encyclopedia
Class : Silicates
Subclass : Phyllosilicates
Crystal System : Monoclinic
Chemistry : (Ca0.5,Na)0.3Al2(Si,Al)4O10(OH)2 nH2O
Rarity : Common
Beidellite is a hydrated phyllosilicate from the smectite group. It is a naturally white clay which is most often colored pink to brownish, or grey-pink ; it presents itself like most clays in earthy, compact and unctuous masses. It owes its name to its place of discovery : Beidell (Colorado, USA). Beidellite is a silicate weathering mineral that typically forms through the weathering of basic and ultrabasic igneous rocks, but can also result from the hydrothermal weathering of plagioclases in hydrothermal deposits, including copper-bearing porphyries. Beidellite is, along with montmorillonite and saponite, one of the main constituents of bentonite.
Main photo : Beidellite from Cameron, Arizona, USA © Chris Emproto
Twinning and special crystallizations
No known twin for this mineral species.
Fakes and treatments
No fake or treatments identified for this mineral species, but difficult to identify without heavy laboratory equipment.
Hardness : 1 to 2
Density : 2 to 3
Fracture : Irregular
Trace : White
TP : Translucent
RI : 1.494 to 1.533
Birefringence : 0.032
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None
Solubility : Insoluble
Magnetism : None
Radioactivity : None