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

No twinning known for this mineral species.

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.