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Formula: Ca5(SiO4)2(CO3)
Nesosilicate (insular SiO4 groups)
Crystal System: Monoclinic
Specific gravity: 3.014 measured, 3.025 calculated
Hardness: 5
Streak: white
Colour: colourless, grey-white, lilac-grey
Environments:
Spurrite is a common component of magnesian skarn at the contact
zone between
limestone and diorite.
Localities
There are two co-type localities, the Terneras Mine, Velardeña, Velardeña District, Cuencamé Municipality, Durango,
Mexico, and the paraspurrite type locality, Darwin, Darwin Mining District, Darwin Hills, Inyo County, California, USA.
At the type localities spurrite occurs as granular masses which resemble crystallised
marble, formed by high-temperature thermal metamorphism along the contact
between carbonate rock and mafic magma. Associated minerals include magnetite,
gehlenite, garnet and
calcite
(Mindat).
Spurrite from Darwin - Image
Alteration
dellaite and calcite to
spurrite and H2O
2Ca6(Si2O7)(SiO4)(OH)2 + 3CaCO3 ⇌
3Ca5(SiO4)2(CO3) + 2H2O
Higher temperatures favour the forward reaction
(MM 34.1.1-16).
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
tilleyite to spurrite and CO2
Ca5Si2O7(CO3)2 ⇌ Ca5(SiO4)2(CO3)
+ CO2
At higher temperatures favour the forward reaction
(MM 34.1.1-16).
wollastonite and spurrite to
rankinite and CO2
4CaSiO3 + Ca5(SiO4)2(CO3) ⇌ 3Ca3Si2O7
+ CO2
Higher temperatures favour the forward reaction
(MM 34.1.1-16).
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