Garronite Subgroup

garronite

olivine

zeolite

phillipsite

The garronite subgroup includes:
Garronite-Ca: Ca₃(Al₆Si₁₀O₃₂).14H₂O
Garronite-Na: Na₆(Al₆Si₁₀O₃₂).8.5H₂O

These minerals are tectosilicates (framework silicates), members of the 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
Environments:

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).

Localities

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).

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