Margarite

phyllosilicate

paragonite

Formula: CaAl2(Al2Si2O10)(OH)2 phyllosilicate (sheet silicate), mica group
Forms a solid solution series with paragonite
Specific gravity: 3.0 to 3.1
Hardness: 3½ to 4½ on {001}, 6 perpendicular to {001}
Streak: White
Colour: Greyish, pale pink, yellow, green. Colourless in thin section.
Solubility: Only partially decomposed by boiling acids
Environments:

Pegmatites
Metamorphic environments

Margarite occurs typically in low to medium grade metamorphic deposits as an alteration product of corundum, also in chlorite and mica schist with staurolite and schorl. It is typically associated with corundum and paragonite or muscovite (AM 61.699-709), and also with diaspore, tourmaline, staurolite, glaucophane, chlorite, manganite, spinel, andalusite, calcite and quartz. It is a mineral of the blueschist, prehnite-pumpellyite, greenschist and amphibolite facies.

At Gibralta, Western Australia, margarite occurs embedded in corundum (Dana).

At Mount Yatyrgvata, northern Caucasus, Russia, sodium-rich margarite occurs at a pegmatite- amphibolite intrusion boundary (Dana).

Near Ferrercairn village, Glen Esk, Scotland, UK, margarite occurs as pseudomorphs after kyanite and contains considerable paragonite in solid solution (AM66.213-216).

Near Meadow Valley, Plumas County, California, USA, margarite occurs with corundum (Dana).

At Emery mines, Chester, Hampden County, Massachusetts, USA, margarite occurs with corundum, magnetite and diaspore (Dana).

Alteration

kyanite and zoisite to margarite and anorthite
2Al2O(SiO4) + 2Ca2Al3[Si2O7][SiO4]O(OH) ⇌ CaAl2(Al2Si2O10)(OH)2 + Ca(Al2Si2O8)
The equilibrium temperature for this reaction at 6 kbar pressure is about 520oC (amphibolite facies), and at 9 kbar it is about 675oC (amphibolite facies). At any pressure the equilibrium is displaced to the right at higher temperatures, and to the left at lower temperatures (SERC, AM61.699-709).

lawsonite to margarite, zoisite and wairakite and H2O
6CaAl2(Si2O7(OH)2.H2O ⇌ CaAl2Si2Al2O10(OH)2 + 2Ca2Al3[Si2O7][SiO4]O(OH) + Ca(Si4Al2)O10.2H2O + 8H2O
Increasing temperature favours the forward reaction (AM61.699-709).

lawsonite to zoisite, margarite, quartz and H2O
5CaAl2(Si2O7)(OH)2.H2 ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + CaAl2(Al2Si2O10)(OH)2 + 2SiO2 + 8H2O
The equilibrium temperature for this reaction at 6.5 kbar pressure is about 425oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and corundum to margarite and H2O
CaAl2(Si2O7(OH)2.H2O + Al2O3 ⇌ CaAl2Si2Al2O10(OH)2 + H2O
Increasing temperature favours the forward reaction (AM61.699-709).

lawsonite and diaspore to margarite and H2O
CaAl2(Si2O7)(OH)2.H2O + 2AlO(OH) ⇌ CaAl2(Al2Si2O10)(OH)2 + 2H2O
The equilibrium temperature for this reaction at 10 kbar pressure is about 460oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and kaolinite to margarite, pyrophyllite and H2O
CaAl2(Si2O7)(OH)2.H2 + 2Al2Si2O5(OH)4 ⇌ CaAl2(Al2Si2O10)(OH)2 + Al2Si4O10(OH)2 + 4H2O
The equilibrium temperature for this reaction at 5 kbar pressure is about 360oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and kaolinite to margarite, quartz and H2O
CaAl2(Si2O7)(OH)2.H2 + Al2Si2O5(OH)4 ⇌ CaAl2(Al2Si2O10)(OH)2 + 2SiO2 +3H2O
The equilibrium temperature for this reaction at 2 kbar pressure is about 300oC (prehnite-pumpellyite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and kaolinite to margarite and wairakite and H2O
2CaAl2(Si2O7(OH)2.H2O + Al2Si2O5(OH)4 ⇌ CaAl2Si2Al2O10(OH)2 + Ca(Si4Al2)O10.2H2O + 3H2O
Increasing temperature favours the forward reaction (AM61.699-709).

lawsonite and kyanite to margarite, pyrophyllite and H2O
3CaAl2(Si2O7)(OH)2.H2 + 4Al2OSiO4 ⇌ 3CaAl2(Al2Si2O10)(OH)2 + Al2Si4O10(OH)2 + 2H2O
The equilibrium temperature for this reaction at 6.5 kbar pressure is about 390oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and kyanite to margarite, quartz and H2O
CaAl2(Si2O7)(OH)2.H2 + Al2OSiO4 ⇌ CaAl2(Al2Si2O10)(OH)2 + SiO2 + H2O
The equilibrium temperature for this reaction at 8 kbar pressure is about 450oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and margarite to zoisite, kyanite and H2O
3CaAl2(Si2O7)(OH)2.H2 + CaAl2(Al2Si2O10)(OH)2 ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + 2Al2OSiO4 + 6H2O
The equilibrium temperature for this reaction at 10 kbar pressure is about 500oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (AM61.699-709).

lawsonite and pyrophyllite to margarite and quartz and H2O
CaAl2(Si2O7(OH)2.H2O + Al2Si4O10(OH)2 ⇌ CaAl2Si2Al2O10(OH)2 + 4SiO2 + 2H2O
Increasing temperature favours the forward reaction (AM61.699-709).

margarite to corundum, anorthite and H2O
CaAl2(Al2Si2O10)(OH)2 ⇌ Al2O3 + Ca(Al2Si2O8)
The equilibrium temperature for this reaction at 6 kbar pressure is about 610oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

margarite to corundum, zoisite, kyanite and H2O
4CaAl2(Al2Si2O10)(OH)2 ⇌ 3Al2O3 + 2Ca2Al3[Si2O7][SiO4]O(OH) + 2Al2OSiO4 + 3H2O
The equilibrium temperature for this reaction at 10 kbar pressure is about 650oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC, AM61.699-709).

margarite and quartz to anorthite, andalusite and H2O
CaAl2(Al2Si2O10)(OH)2 + SiO2 ⇌ Ca(Al2Si2O8) + Al2OSiO4 + H2O
The equilibrium temperature for this reaction at 2 kbar pressure is about 440oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures. (SERC, AM61.699-709).

margarite and quartz to anorthite, kyanite and H2O
CaAl2(Al2Si2O10)(OH)2 + SiO2 ⇌ Ca(Al2Si2O8) + Al2OSiO4 + H2O
The equilibrium temperature for this reaction at 5 kbar pressure is about 520oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC, AM61.699-709).

margarite and quartz to zoisite, kyanite and H2O
4CaAl2(Al2Si2O10)(OH)2 + 3SiO2 ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + 5Al2OSiO4 + 3H2O
The equilibrium temperature for this reaction at 8 kbar pressure is about 510oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures. At moderate pressure the assemblage margarite and quartz is stable within a temperature range of 300 to 560oC. This explains why the assemblage quartz and margarite is restricted to low- and medium-grade metamorphic rocks. At higher pressure this assemblage gives way to the high-pressure assemblage zoisite and kyanite, as reported from many greenschist to amphibolite facies eclogites (AM61.699-709).

wairakite to zoisite and margarite and quartz and H2O
5Ca(Si4Al2)O10.2H2O ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + CaAl2Si2Al2O10(OH)2 + 12SiO2 + 8H2O
Increasing temperature favours the forward reaction (AM61.699-709).

wairakite and kaolinite to margarite and quartz and H2O
Ca(Si4Al2)O10.2H2O + Al2Si2O5(OH)4 ⇌ CaAl2Si2Al2O10(OH)2 + 4SiO2 + 3H2O
Increasing temperature favours the forward reaction (AM61.699-709).

wairakite and pyrophyllite to margarite, quartz and H2O
Ca(Si4Al212.2H2O + Al2Si4O10(OH)2 ⇌ CaAl2Si2Al2O10(OH)2 + 6SiO2 + 2H2O
Increasing temperature favours the forward reaction (SERC).

wairakite, zoisite and margarite to anorthite and H2O
Ca(Si4Al2)O10.2H2O + 2Ca2Al3[Si2O7][SiO4]O(OH) + CaAl2Si2Al2O10(OH)2 ⇌ Ca(Al2Si2O8) + H2O
Increasing temperature favours the forward reaction (AM61.699-709).

zoisite, kyanite and diaspore to margarite
Ca2Al3[Si2O7][SiO4]O(OH) + Al2OSiO4 + 3AlO(OH) ⇌ 2CaAl2(Al2Si2O10)(OH)2
The equilibrium temperature for this reaction at 12 kbar pressure is about 480oC (blueschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

zoisite, margarite and quartz to anorthite and H2O
2Ca2Al3[Si2O7][SiO4]O(OH) + CaAl2(Al2Si2O10)(OH)2 + 2SiO2 ⇌ 5Ca(Al2Si2O8) + 2H2O
The equilibrium temperature for this reaction at 6 kbar pressure is about 540oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

Common impurities: Na,Mg,Cr,Li,Mn,Fe,K,Ba,Sr,H2O

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