Images
Formula: Ca6Si6O17(OH)2
Inosilicate (chain silicate)
Crystal System: Monoclinic
Specific gravity: 2.70 to 2.72 measured, 2.71 calculated
Hardness: 6½
Streak: white
Colour: colourless, white, grey, pale pink
Common impurities: Fe, Mn, H2O
Environments:
Xonotlite occurs in veinlets in serpentine or in
contact metamorphic deposits within
limestone.
Localities
The type locality is Tetela de Ocampo, Tetela de Ocampo Municipality, Puebla, Mexico.
Xonotlite from Tetela de Ocampo - Image
Alteration
johannsenite and H2O to
rhodonite and xonotlite
6CaMnSi2O6 + H2O → 6Mn2+SiO3 +
Ca6Si6O17(OH)2
At Pueblo, Mexico, johannsenite occurs in calcite
veins in
rhyolite and is altered to rhodonite
and xonotlite
according to the above equation
(DHZ 2A p421).
Alteration
xonotlite to wollastonite and H2O
Ca6Si6O17(OH)2 ⇌ 6CaSiO3 + H2O
Higher temperatures favour the forward reaction
(MM 34.1.1-16).
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