Kalsilite

minerals

melilite

leucite

nepheline

Formula:KAlSiO4
Tectosilicate (framework silicate), feldspathoid
Specific gravity: 2.6
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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