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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
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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