SAPONITE
Class : Silicates
Subclass : Phyllosilicates
Crystal system : Monoclinic
Chemistry : (Ca,Na)0.3(Mg,Fe)3(Si,Al)4O10(OH)2 4H2O
Rarity : Common
Saponite is a magnesium hydrated phyllosilicate of the smectite group. It is a silicate alteration mineral that is generally formed by alteration of basic and ultrabasic igneous rocks, but can also result from hydrothermal alteration of plagioclase in hydrothermal deposits, sometimes in skarns. Its name comes from the Latin sapo (soap) in allusion to the soft and greasy appearance of its aggregates in small scales. It occurs like most clays in earthy, compact, unctuous masses. The crystals are microscopic, pseudohexagonal in appearance. It is a white to yellowish clay, sometimes colored light yellow, greenish or reddish. Saponite is, with beidellite, montmorillonite and nontronite, one of the main constituents of bentonite.
Main photo : Sampleite from La Farola Mine, Atacama, Chile © Uwe Haubenreisser
Saponite in the World and in France
Twinning
No twinning known for this mineral species.
Fakes and treatments
No fakes listed for this mineral species.
Hardness : 1.5 to 2
Density : 2.24 to 2.30
Fracture : Undetermined
Streak : White
TP : Translucent
RI : 1.479 to 1.527
Birefringence : 0.032 to 0.037
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None
Solubility : Sulfuric acid
Magnetism : NoneRadioactivity : None