PARAGONITE

    Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Monoclinic
    Chemistry : NaAl2(Si3Al)O10(OH)2
    Rarity : Uncommon to fairly common

Paragonite is an uncommon mineral from the micas group. It is the sodium equivalent of muscovite, but the replacement of potassium by sodium being limited, there is no solid solution with the latter. It is also much less common than this and appears mainly in poorly metamorphic schists and mica-schists, in biotite and muscovite gneisses and in certain glaucophane rocks, where it can be locally abundant. Its name comes from the Greek paragein (to make a mistake) because the mineral resembles talc. Paragonite most often appears in small flakes or scales, rarely in flattened crystals on {001}. Its luster is pearly on the cleavage and its color varies : colorless, grayish to greenish, sometimes more distinct green.


Main photo : Paragonite, kyanite and staurolite from Pizzo Forno, Switzerland © Nathan Harrison

Paragonite in the World

Very beautiful paragonite - kyanite - staurolite associations exist in the mica-schists of the Swiss Alps, notably at Pizzo Forno (St-Gothard Massif). Miass, in Mount Ilmen (Urals, Russia) also provided good, well crystallized specimens.

Paragonite in France

In France, paragonite is known in the Alps, particularly in St-Jean-de-Maurienne (Savoie) and Briançon (Hautes-Alpes), on the island of Groix (Morbihan) and in Corsica.

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 2.5 to 3
Density : 2.85
Fracture : Micaceous
Streak : White

TP : Translucent to transparent
RI : 1.564 to 1.609
Birefringence : 0.036
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Insoluble

Magnetism : NoneRadioactivity : None