STELLERITE

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Orthorhombic
    Chemistry : CaAl2Si7O18 7H2O
    Rarity : Rare to uncommon


Stellerite is a fairly rare mineral of the zeolite group, but perhaps less rare than one might think. It is found, like most zeolites, in cavities and fractures of volcanic rocks, particularly basalts. It was named in honor of the German explorer Georg Wilhelm Steller. The elongated crystals are frequently grouped into spheres with a radiate texture measuring up to 12 cm in diameter. It is colorless to white, sometimes pinkish or yellowish.

Main photo : Stellerite from Aurangabad, Maharashtra, India © Dan Weinrich

Stellerite from Braen Quarry, Haledon, New Jersey, USA © Frank A. Imbriacco III
Stellerite from Gunnedah, Pottinger Co., Australia © Volker Betz
Stellerite from Sarbai, Rudny, Kazakhstan © Boris Z. Kantor
Stellerite on epidote from Trimouns, Ariège, France © Yannick Vessely

Stellerite in the World

Stellerite accompanies other zeolites in the most famous sites in the world : the Hindu Dekkan (Poona, Bombay, Nasik), which has produced extraordinary specimens of stellerite (spheres exceeding 10 cm in diameter) and the American basalts of New Jersey (notably Paterson) and New York. Large crystals have also been discovered in Australian basalts (Gunnedah, Corop, Dookie, etc...). The Sardinian sites of Villanueva Monteleone and Osilo have the best crystals in Europe, while Rudny (Kazakhstan) has produced very original pink-orange stellerite crystals.

Stellerite in France

In France, stellerite is identified in St-Jean-de-Maurienne (Savoie) as well as in Trimouns (Ariège).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species. It is however visually impossible to differentiate between stellerite and stilbite. Indeed, stellerite can occur as individual crystals, as well as fan-shaped, bow-tie, sheaf and sphere-shaped aggregates that are also typical of stilbite. Stellerite has often been tentatively differentiated from stilbite on the basis of its morphology. But the only reliable method to distinguish these two minerals is a chemical analysis capable of identifying Na, in combination with X-ray diffraction to highlight the orthorhombic symmetry.



Hardness : 4.5
Density : 2.13
Fracture : Undetermined
Streak : White


TP : Translucent to transparent
RI : 1.485 to 1.498
Birefringence : 0.013
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None


Solubility : -

Magnetism : NoneRadioactivity : None