Scawtite

scawtite

melilite

spurrite

tobermorite

Images

Formula: Ca7(Si3O9)2(CO3).2H2O
Cyclosilicate (ring silicate)
Specific gravity: 2.71
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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