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

Worldwide widespread in soils and superficial alterites on basic and ultrabasic rocks, saponite never forms macroscopic crystals or specimens with aesthetic value.

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

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