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Formula: Ca7(Si3O9)2(CO3).2H2O
Cyclosilicate (ring silicate)
Crystal System: Monoclinic
Specific gravity: 2.71 measured, 2.74 calculated
Hardness: 4 to 5
Streak: White
Colour: Colourless
Solubility: Soluble in cold dilute hydrochloric acid with formation of a gelatinous residue (Dana)
Common impurities: Ti,Al,Fe,Mn,Mg
Environments
Metamorphic environments
Hydrothermal environments
Scawtite occurs as a late-stage hydrothermal mineral veining skarn formed from
contact metamorphism of limestone.
Associated minerals include melilite, spurrite,
tobermorite, thomsonite,
larnite, grossular,
bultfonteinite, calcite,
analcime, foshagite and
hillebrandite
(HOM).
Localities
At the Fuka mine, Fuka, Bicchu-cho, Takahashi City, Okayama Prefecture, Japan, the deposit is a high-temperature,
boron-containing skarn
(R&M 965.395). Scawtite occurs with
grossular, vesuvianite and
calcite
(Dana).
At Tokatoka, Kaipara District, Northland Region, New Zealand, scawtite occurs with larnite,
spurrite, tobermorite,
gehlenite, garnet,
vesuvianite, calcite and
wollastonite
(Dana).
At the type locality, Scawt Hill, Larne, County Antrim, Northern Ireland, UK, scawtite occurs in
contact metamorphosed limestone and
dolostone intruded by dolerite. Associated
minerals include melilite, bultfonteinite,
calcite, thomsonite and other
zeolites
(AM 20.403, Mindat, Dana).
At Ballycraigy, Larne, County Antrim, Northern Ireland, UK scawtite occurs in a vesicle in larnite
rocks in association with tobermorite
(AM 40.510-514).
At Crestmore quarries, Crestmore, Riverside county, California, USA, scawtite occurs in thin veins in a matrix of massive
diopside-wollastonite-spurrite
rock. In general, scawtite is the latest mineral to form in the veins in which it appears, overlying and enveloping
calcite crystals. Associated with the massive scawtite in one or two of the veins, are fine-grained
sugary aggregates of bultfonteinite
(AM 40.505-509).
Scawtite and calcite are the earliest minerals in the fractures and may be encrusted by
tobermorite, jennite or both
(AM 51.56).
Alteration
Scawtite forms as pseudomorphs after spurrite, and
it alters to tobermorite and tacharanite
(Dana).
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