FRESNOITE

    Class : Silicates
    Subclass : Sorosilicates
    Crystal system : Tetragonal
    Chemistry : Ba2TiOSi2O7
    Rarity : Very rare

Fresnoite is an extremely rare silicate of barium and titanium. It is found in metamorphic rocks, notably gneisses and pyrometasomatic quartzites. It owes its name to its location of discovery : the region of Big Creek and Rush Creek in Fresno County (California). Fresnoite forms small, tabular to slightly elongated tetragonal crystals, generally millimeter-sized, of yellow to orange color.

Main photo : Fresnoite from Junnila Mine, California, USA © Rob Lavinsky

Fresnoite from Junnila Mine, California, USA © Rob Lavinsky
Fresnoite on analcime from Junnila Mine, California, USA © Rob Lavinsky
Fresnoite from Löhley, Eifel Volcanic Fields, Germany © Fred Kruijen
Fresnoite from Graulay Quarry, Germany © Volker Heck

Fresnoite in the World

Fresnoite is mainly a Californian mineral which appears in metamorphic rocks rich in barium, this probably emanating from nearby granitic intrusions (localities of Big Creek and Rush Creek). Fresnoite is also present in hydrothermal veins in California (Gem Mine, famous for its benitoite and neptunite). The best known crystals measure over 1.5 cm and come from Junnila Mine. Finally, it is reported in Germany in the Eifel, in thin fissures of pneumatolytic origin.

Fresnoite in France

Fresnoite is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 3 to 4
Density : 4.43
Fracture : Irregular
Streak : White

TP : Translucent
RI : 1.765 to 1.775
Birefringence : 0.010
Optical character : Uniaxial -
Pleochroism : Visible
Fluorescence : Yellow under short UV

Solubility : -


Magnetism : None
Radioactivity : None

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