Lavenite - Encyclopedia

    Class : Silicates
    Subclass : Sorosilicates
    Crystal system : Monoclinic
    Chemistry : Na2(Mn,Ca,Fe)ZrSi2O7(O,OH,F)2
    Rarity : Uncommon

Lavenite is a silicate of alkaline rocks deficient in silica, notably nepheline syenites and their pegmatites, where it accompanies nepheline, eudialyte, titanite, apatite and aegyrine. Its name derives from its discovery location : Laven Island (Norway). Lavenite typically ranges in color from light yellow to black-brown, but can also be exceptionally colorless. When lavenite is not massive, its elongated crystals are frequently united into radiated acicular aggregates measuring up to 2 cm.

Main photo : Lavendulan from Preamimma Mine, Callington, Australia © Jean-Pierre Barral

Lavendulan from María Josefa Mine, Almería, Spain © Pascal Chollet
Lavendulan from Clara Mine, Germany © Michael Förch
Lavendulan from Preamimma Mine, Callington, Australia © Gianfranco Ciccolini
Lavendulan from Cap Garonne, Var, France © Pascal Chollet

Lavenite in the World

Lavenite is known from most of the large alkaline districts of the world : nepheline syenites from the Kola Peninsula (Russia) and the Los Islands (Guinea), alkaline syenites from southern Norway (Langesundsfjord), Mont St-Hilaire (Quebec), etc... Although rarer in undersaturated volcanic rocks, lavenite is also present in the alkaline basalts of the Eifel volcanic complex in Germany (Lake Laacher) notably in epitaxy on wöhlerite, and in the islands from Tenerife (Canary Islands) and Boa Vista (Cape Verde).

Lavenite in France

In France, lavenite is reported in an intrusion of nepheline syenite at Fitou near Narbonne (Aude), at Cristinacce near Ajaccio (South Corsica) as well as in Velay (Haute-Loire).

Twinning

Polysynthetic twins are known on {100}.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 6
Density : 3.4 to 3.55
Fracture : Irregular
Streak : Yellow to brown

TP : Translucent to transparent
RI : 1.670 to 1.720
Birefringence : 0.050
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None

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