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Formula:KAlSiO4
Tectosilicate (framework silicate), feldspathoid
Crystal System: Hexagonal
Specific gravity: 2.59 to 2.62 measured
Hardness: 6
Streak: White
Colour: colourless, grey, grey white, white
Common impurities: Fe,Mg,Ca,Na
Environments:
Plutonic igneous environments
Volcanic igneous environments
Kalsilite occurs in the groundmass of some potassium-rich and silica-deficient lavas and
tuffs; it is rare in syenite; it may be formed
by the breakdown of silica-rich leucite in alkalic
ultramafic rocks. It has also been found in a
granulite facies emery deposit.
Kalsilite is associated or intergrown with nepheline. Other associates include
olivine, melilite,
clinopyroxene, phlogopite and
leucite
(HOM).
Localities
At the ultramafic Batbjerg intrusion, eastern Greenland, Denmark, kalsilite is
intergrown with K-feldspar
(Dana).
At Pian di Celle, San Venanzo, Italy, kalsilite occurs in rock containing pyroxene,
olivine, phlogopite and
leucite
(AM 28.62).
At the Yakshimsk pluton, Russia, kalsilite occurs in syenite
(Dana).
At the type locality is Kamengo, Gomba District, Central Region, Uganda, kalsilite occurs in potash-rich
ultrabasic lavas containing varying proportions of
olivine, melilite,
diopsidic augite and
leucite. Other minerals associated with kalsilite are
phlogopite and a zeolite related to
harmotome
(AM 28.62).
At the Baruta crater, Nyiragongo area, Zaire, kalsilite occurs as nepheline -
kalsilite phenocrysts
(Dana).
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