Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Monoclinic
    Chemistry : Na_0.3Fe₂(Si,Al)₄O₁₀(OH)₂ nH₂O
    Rarity : Common

Nontronite is a hydrated phyllosilicate from the smectite group. It is a silicate alteration mineral that generally forms by weathering of basic and ultrabasic igneous rocks, and can also result from hydrothermal alteration of plagioclases in hydrothermal deposits. Its name comes from its discovery location : Nontron near St-Pardoux (Dordogne, France). It is an olive green to dark green and brown-green colored clay, sometimes yellow or rust. It appears like most clays in earthy, compact and creamy masses. It is very widespread in soils and surface alterites and never forms macroscopic crystals or specimens of aesthetic value. It is one of the main constituents of bentonite, it is also used as an ion exchange material, saponifier, degreaser and in the construction industry where it constitutes a powerful absorbent.

Main photo : Nontronite from Kempirsai Cr deposit, Kazakhstan © Pavel Kartashov

No twins known for this mineral species.

No fakes recorded for this mineral species.