Clinoptilolite - Encyclopedia

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Monoclinic
    Chemistry : (Ca,K,Na)3Al3Si15O36 11.5H2O
    Rarity : Rare to uncommon

Clinoptilolite is a mineral from the zeolite group, chemically very close to heulandite, of which it was long considered a variety. Its name is linked to its monoclinic crystal system and its chemical similarity to ptilolite. It is found in the cavities of andesitic to rhyolitic lavas, which have provided the most beautiful crystals, as a product of devitrification of volcanic glasses, sometimes in Alpine clefts and more rarely in sedimentary domains. It appears in lamellar crystals, generally small (1 cm), or in finely grained masses, colorless or rarely orange-red. Zeolites have important industrial applications, based on their channel structure which allows molecular sieving (used in petroleum cracking), the presence of water which can be evacuated by heating (hydration and dehydration properties ), the existence of weakly bonded cations which give them very important ion exchange properties. To satisfy these industrial needs, artificial zeolites are produced in large quantities, clinoptilolite with chabazite and heulandite or stilbite being the only ones sufficiently abundant and pure to constitute exploitable deposits.

Main photo : Clinoptilolite from Cape Lookout Quarry, Oregon, USA © Daniel Russell

Clinoptilolite from Richardson Ranch, Oregon, USA © Volker Betz
Clinoptilolite from Rodalquilar, Andalusia, Spain © Christian Rewitzer
Clinoptilolite from the Weitendorf basalt quarry, Austria © Christian Auer
Clinoptilolite-Ca on lussatite from the Mine des Rois, Dallet, Puy-de-Dôme, France (GSE)

Clinoptilolite in the World

The volcanic rocks of Oregon (Agathe Beach, Bend, etc...) have yielded the most beautiful specimens of clinoptilolite, lamellar crystals of 1 cm, but this mineral is reported in many other American states (Arizona, California, Wyoming ...). Good crystals have also been extracted from the Italian Alpine clefts of Val di Fasa and Alpe di Siusi in Trentino. It is also found in Honcova Hurka Hill (Czech Republic) in red crystals.

Clinoptilolite in France

In France, we find clinoptilolite-Ca in 100 µm crystals associated with lussatite from Mine des Rois near Dallet (Puy-de-Dôme).


No twin known for this mineral species.

Due to its occasionally sedimentary deposits, clinoptilolite can line the cavities of fossil organisms, this is the case at Bushy Point near Kaipara Harbor (New Zealand) where it has been reported on fossil marine gastropods.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 3.5 to 4
Density : 2.1
Fracture : Irregular to sub-conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.476 to 1.497
Birefringence : 0.003 to 0.006
Optical character : Biaxial (+/-)
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None


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