ZEOPHYLLITE

    Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Hexagonal
    Chemistry : Ca4Si3O8(OH,F)4 2H2O
    Rarity : Rare

Zeophyllite is a calcium silicate of rocks poor or deficient in silica. It is thus found as an alteration mineral of basalts, in hydrothermal veins cutting nepheline syenites and in marble xenoliths included in certain nepheline syenites. Its name comes from the Greek zein (to boil) and phullon (leaf), in allusion on the one hand to the foliated and hemispherical shape of its crystals and on the other hand to the boiling which occurs by evaporation of water vapor by heating. Zeophyllite occurs in lamellar crystals, frequently gathered in hemispherical to spherical aggregates with a radiate texture, not exceeding 1 cm; it is also found in botryoidal to spherolitic encrustations. Its color is white.

Main photo : Zeophyllite from Schellkopf, Eifel, Germany © Pascale & Daniel Journet

Zeophyllite in the World

Zeophyllite is found in the nepheline syenites of Khibiny (Russia) and Mont St-Hilaire (Canada). It is also found in the cavities of many basalts in the Czech Republic (Litomerice, Teplice) and Germany (Brenk near Lake Laacher), and in the recent lavas of the Somma (Italy).

Right photo : Zeophyllite from Caspar quarry, Eifel, Germany © Christof Schäfer


Zeophyllite in France

Zeophyllite is not present in the French underground.

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3
Density : 2.74 to 2.76
Fracture : Undetermined
Streak : White

TP : Translucent
RI : 1.560 to 1.577
Birefringence : 0.005 to 0.008
Optical character : Uniaxial -
Pleochroism : None
Fluorescence : None

Solubility : Acids

Magnetism : NoneRadioactivity : None