Formula: Na2SrAl4Si4O16
Tectosilicate (framework silicate), feldspar group, forms a series with
banalsite
Crystal System: Orthorhombic
Specific gravity: 2.95 measured, 2.95 calculated
Hardness: 6½
Streak: White
Colour: White
Common impurities: Ba,Ca,Sr
Environments
Stronalsite occurs in basic tuff xenoliths, associated with
pectolite, slawsonite,
albite, calcite,
aragonite, natrolite,
thomsonite, prehnite,
datolite, rosenhahnite and
vuagnatite
(HOM, Webmin).
Localities
At Čertův mlýn, Bludovice, Nový Jičín, Nový Jičín District, Moravian-Silesian Region, Czech Republic, Barium- and
calcium- rich stronalsite occurs rarely as pseudomorphs, which
are probably after nepheline, and is found in hydrothermally altered
strontium-enriched leucocratic (light-coloured) dykes or streaks hosted
by mesocratic (having nearly equal light and dark constituents)
amphibole–pyroxene
teschenite. In addition to stronalsite, the
pseudomorphs consist of
slawsonite, celsian,
biotite, muscovite,
alkali feldspar,
natrolite and
thomsonite-Ca. The surrounding groundmass is rich in
alkali feldspars and
zeolites and sporadically also contains
amphibole phenocrysts,
chloritised
biotite, fluorapatite and
other accessory and/or secondary minerals.
The main source of Sr was probably primary magmatic
plagioclase that underwent hydrothermal alteration by post-magmatic
high-temperature brines mixed with fluids of external origin. It is estimated that stronalsite crystallised
at about 250–320°C and pressure less than 100 MPa (1 Kbar).
(MM 89.357–369).
Stronalsite from Čertův mlýn -
Image
At the type locality, the Tanaka Olivine Mining Company quarry, Rendai, Kochi City, Kochi Prefecture, Japan, stronalsite
occurs as aggregates of crystals to 1 mm across, in association with slawsonite and
pectolite in veinlets cutting rodingite
in the serpentinite quarry. Associated vein minerals include
prehnite, xonotlite,
grossular and its variety hydrogrossular and
natrolite
(AM 72.226).
At Mt Ohsa, Niimi City, Okayama, Japan, stronalsite occurs in veinlets and grains in
jadeitic aggregates within serpentinite
(HOM, Dana).
Stronalsite from Mt Ohsa - Image
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