Jennite

minerals

afwillite

tobermorite

monticellite

Formula: Ca9(Si3O9)2(OH)6.8H2O
Sorosilicate (Si2O7 groups), cuspidine - wöhlerite group
Specific gravity: 2.32 to 2.33
Hardness: 3½
Streak: White
Colour: White
Common impurities: Ti,Al,Fe,Mn,Mg,Na,K,P
Environments

Metamorphic environments

Jennite is a late stage mineral in metamorphosed limestone (Webmin).

Localities

At Maroldsweisach, Bavaria, Germany, jennite occurs in xenoliths in basalt (Dana).

At Fuka, Japan, jennite is associated with afwillite, oyelite and spurrite (HOM).

At the type locality, the Crestmore quarries, Riverside county, California, USA, jennite occurs as a late stage mineral partially filling open spaces in fractured calcite - monticellite - hercynite and vesuvianite - wollastonite contact metamorphic rock. The monticellite has been altered to serpentine plus calcite for five or more centimeters on either side of the fractures although the wollastonite in the vesuvianite - wollastonite rock has been unaffected. Jennite is always associated with tobermorite and is occasionally found with scawtite and calcite. Scawtite and calcite are the earliest minerals in the fractures and may be encrusted by tobermorite or jennite or both (AM 51.56-74.).

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