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Formula: Ca9(Si3O9)2(OH)6.8H2O
Sorosilicate (Si2O7 groups)
Crystal System: Triclinic
Specific gravity: 2.32 to 2.33 measured, 2.325 calculated
Hardness: 3½
Streak: White
Colour: White
Common impurities: Ti,Al,Fe,Mn,Mg,Na,K,P
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, the deposit is a high-temperature,
boron-containing skarn
(R&M 965.395). 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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