Garronite is a series with end members:
Garronite-Ca: Ca3(Al6Si10O32).14H2O
Garronite-Na: Na6(Al6Si10O32).8.5H2O
These minerals are tectosilicates (framework silicates), zeolite group.
Garronite-Na was approved as a new mineral in 2015. Previously "garronite" had been the species name of the mineral now renamed "garronite-Ca".
Specific gravity: 2.13 to 2.18
Hardness: 4½ to 5
Streak: White
Colour: Colourless, white
Common impurities: Ca: Fe,Ba,K

Basaltic cavities

Garronite is most common in vesicles in basalt and other mafic rocks, often overgrown by or associated with phillipsite, and also as epitaxial overgrowths on phillipsite (Dana).


The Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, is the type locality for garronite-(Na), which occurs in some metamorphic rocks and in sodalite xenoliths (Dana).

In Iceland garronite occurs at numerous localities in lavas rich in phenocrysts of anorthite variety bytownite and in non-porphyritic olivine basalt flows (HOM).

In Russia, near Nevon, on the Angara River, 50km below the Ilim River, Siberia, garronite occurs in dolerite porphyry (HOM).

The Glenariff Valley, Garron Plateau, County Antrim, Ulster, Northern Ireland, UK, is the type locality for garronite-(Ca). The mineral occurs as amygdule ̄fillings in silica-undersaturated olivine basalt flows (HOM).

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