Merwinite

minerals

monticellite

spurrite

xonotlite

Formula: Ca3Mg(SiO4)2
Nesosilicate (insular SiO4 groups)
Specific gravity: 3.15 to 3.32
Hardness: 6
Streak: White
Colour: White, colourless, light green, light grey green
Common impurities: Al, Fe

Metamorphic environments

At the type locality, the Wet Weather Quarry, Sky Blue Hill, Crestmore quarries, Crestmore, Riverside county, California, USA, merwinite is found in high temperature, low pressure contact metamorphic zones within marble, associated with xonotlite, wollastonite, monticellite, larnite, grossular, gehlenite, clintonite and calcite (Mindat).

Alteration

monticellite and spurrite to merwinite and calcite
2CaMg(SiO4) + Ca5(SiO4)2(CO3) ⇌ 2Ca3Mg(SiO4)2 + CaCO3

monticellite, spurrite and quartz to merwinite and CO2
5CaMg(SiO4) + Ca5(SiO4)2(CO3) + SiO2 ⇌ 5Ca3Mg(SiO4)2 + 2CO2

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