Gobbinsite

Images

Formula: Na₅(Si₁₁Al₅)O₃₂.11H₂O
Hydrated tectosilicate, zeolite group
Crystal system: Orthorhombic
Specific gravity: 2.194 measured on a specimen from the type locality, but probably too high because of calcite and other impurities such as copper salts. The calculated value is 2.147.
Hardness: 4
Streak: White
Colour: White, colourless
Common impurities: Fe,Sr,Ba
Environments

Basaltic cavities

Localities

At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada, gobbinsite occurs in cavities in sodalite syenite in an intrusive alkalic gabbro-syenite complex, associated with "tetranatrolite" (discredited in 1999) and serandite (HOM).
Gobbinsite from the Poudrette Quarry - Image

At Kuniga, Nishinoshima, Oki Islands, Okinoshima, Oki District, Shimane Prefecture, Japan, gobbinsite occurs as fibrous crystals in cavities in altered trachybasalt (Japanese Magazine of Mineralogical and Petrological Sciences, 29.4.129-135).

At Punta del Aguila, Playa Blanca, Yaiza, Lanzarote, Las Palmas Province, Canary Islands, Spain, gobbinsite has been found with phillipsite, gonnardite, chabazite and lévyne (Mindat photo).
Gobbinsite from Punta del Aguila - Image

At the type locality, Hills Port, Gobbins, Islandmagee, Co. Antrim, Northern Ireland, UK, amygdaloidal basalt specimens collected from the scree and the cliff face of the coastal escarpment near Hills Port contain fibrous, chalky white gobbinsite that has optical properties and an X-ray pattern distinctly different from any other known naturally occurring zeolite. It occurs in roughly spherical vugs up to 5 mm diameter, either alone or in association with gmelinite of platy habit. In other specimens at this locality vugs in the basalt are filled with chabazite, gonnardite or "tetranatrolite" (discredited in 1999) (MM 46.365-369).
Gobbinsite from Hills Port - Image

At the Basalt quarry, Magheramorne, Glynn, Larne, Co. Antrim, Northern Ireland, UK, gobbinsite is found as a rare filling of vugs and vesicles of amygdaloidal basalts. The cavities containing gobbinsite are composed of compact radiating masses, chalky-white or slightly pink in colour. All analysed vugs containing gobbinsite also contain a variable amount of intimately associated phillipsite. No cavity was found with gobbinsite alone. The other cavities in the altered basalt rock contain calcite and a variety of zeolite minerals including cowlesite, analcime, garronite, gmelinite, gonnardite, thomsonite and natrolite (MM 58.615-620).

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