Garronite-Ca

garronite-Ca

thomsonite

chabazite

heulandite

Images

Formula: Ca3(Al6Si10O32).14H2O
Tectosilicate (framework silicate), garronite subgroup, zeolite group, forms a series with garronite-Na
Formerly garronite; renamed garronite-Ca in 2015 when garronite-Na was discovered.
Crystal System: Tetragonal
Specific gravity: 2.13 to 2.17 measured, 2.201 calculated
Hardness: 4 to 5
Streak: White
Colour: White
Common impurities: Fe,Ba,K
Environments

Basaltic cavities

Localities

At Bæjartindur, Breiðdalur, Fjarðabyggð, Eastern Region, Iceland, garronite-Ca occurs in olivine-basalt lavas and is associated with chabazite and thomsonite-Ca (MM 33.173-186 as garronite).
Garronite-Ca from Iceland - Image

At Mount Skessa, Reyðarfjörður, Fjarðabyggð, Eastern Region, Iceland, garronite-Ca is readily collected from screes from the Graenavatn porphyritic group. Specimens fill amygdales commonly measuring 1 to 2 cm across. The garronite-Ca is usually alone in its amygdale, but occasionally it is accompanied by thomsonite-Ca or heulandite. Other minerals in the basalts are chabazite, levyne and a little hair-like mesolite (MM 33.173-186 as garronite).

At Hánefsstadafjall, Seyðisfjörður, Múlaþing, Eastern Region, Iceland, garronite-(Ca) occurs in olivine-basalt lavas associated with chabazite, thomsonite-Ca and levyne (MM 33.173-186 as garronite).

At the type locality, the Glenariff Valley, Garron Plateau, County Antrim, Ulster, Northern Ireland, UK, garronite-Ca is found fairly abundantly in screes on the steep western slopes of the valley. Zeolites are abundant in amygdales in thin olivine-basalt at this locality; they include chabazite, thomsonite-Ca, analcime, levyne, natrolite and phillipsite. Phillipsite forms well-shaped crystals lining amygdales, and is quite distinct from garronite-Ca, which forms radiating aggregates completely filling the amygdales that it occupies.
Garronite-Ca at this and other localities forms compact radiating aggregates and alone, or with other zeolites, normally completely fills the amygdale in which it occurs. Occasionally it is accompanied by thomsonite-Ca or other zeolites, and when incompletely filling an amygdale phillipsite characteristically coats the surface of the garronite aggregate (MM 33.173-186 as garronite).
Garronite-Ca from the Glenariff Valley - Image

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