Tectosilicate (framework silicate), zeolite group, forms a series with garronite-Ca, previously known as garronite
Specific gravity: 2.19
Colour: Pale yellow to white
Plutonic igneous rocks
Garronite-Na is a relatively new mineral, approved in 2015.
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, garronite-Na occurs in vugs in sodalite syenite as botryoidal masses up to 1.5 mm in size. Associated minerals include aegirine, natrolite, gmelinite and gonnardite (CM 54.1549-1562).
At Shiratobana, Hirado Island, Hirado City, Nagasaki, Japan, silica-rich garronite-Na was found in a cavity with a diameter of about 2 mm in altered basaltic rock. Hirado Island is composed mainly of volcanic andesite and basalt lava accompanied by pyroclastic rocks. More than 10 species of zeolite (chabazite, epistilbite, harmotome, phillipsite, stellerite, stilbite, barrerite, thomsonite, scolecite, mordenite, dachiardite and ferrierite) have been described as occurring in altered volcanic rocks from the Island. The zeolite minerals occur as hydrothermal minerals in the druses and veins of the basaltic and andesitic rocks. The garronite-Na from Shiratobana fills the central part of the cavity and is associated with radial aggregates of epistilbite, which cover the inside of the cavity, suggesting that the garronite-Na crystallised after the formation of the epistilbite (CM.60.1.91-99).
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