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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.
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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