Xonotlite

xonotlite

inosilicate

johannsenite

rhodonite

Images

Formula: Ca6Si6O17(OH)2
Inosilicate (chain silicate)
Specific gravity: 2.7
Hardness: 6½
Streak: white
Colour: colourless, white, grey, pale pink
Common impurities: Fe, Mn, H2O
Environments:

Metamorphic 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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