Kyanite

nesosilicate

sillimanite

Formula: Al2OSiO4 nesosilicate (insular SiO4 groups). Polymorph (same formula, different structure) of andalusite and sillimanite.
Specific gravity: 3.53 to 3.65
Hardness: 5½ to 7
Streak: White
Colour: Blue, green, orange, black
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Environments:

Placer deposits
Metamorphic environments (typical)

Kyanite is a common mineral of high to very high pressure regionally metamorphosed rocks and typically it is found in gneiss and schist. Associated minerals include andalusite and/or sillimanite, garnet, staurolite, talc, mullite, corundum and hornblende (Lauf p180).
It is a common constituent of eclogite, and it also may be found in hornfels and in garnet- omphacite-kyanite occurrences in kimberlite pipes.
Kyanite develops after staurolite and before sillimanite with increasing grade of metamorphism. It is a characteristic mineral of the amphibolite and granulite facies and it is also a mineral of the greenschist, blueschist and eclogite facies.

Alteration

Aluminium silicate stability diagram andalusite, sillimanite and kyanite are polymorphs (same formula, different structure); they are in equilibrium at a pressure of 3.75 kbar and temperature 504oC (amphibolite facies) (AM78.298-315).
Kyanite is unstable at low pressure.

anorthite to grossular, kyanite and quartz
3CaAl2 Si2O8 → Ca3Al2(SiO4)3 + 2Al2OSiO4 + SiO2
At 20 kbar pressure the equilibrium temperature is about 1,000oC and at 30 kbar it is about 1,400oC

diaspore and quartz to kyanite and H2O
2AlO(OH) + SiO2 ⇌ Al2OSiO4 + H2O
The equilibrium temperature for this reaction at 10 kbar pressure is about 420oC (greenschist facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

enstatite and kyanite to spinel and cordierite
5Mg2Si2O6 + 10Al2OSiO4 ⇌ 2MgAl2O4 + 4Mg2Al4Si5O18
Increasing temperature favours the forward reaction (SERC).

enstatite, kyanite and quartz to cordierite
Mg2Si2O6 + 2Al2OSiO4 + SiO2 ⇌ Mg2Al4Si5O18
At 6 kbar pressure the equilibrium temperature is about 475oC (greenschist facies). The equilibrium moves to the right at higher temperatures and to the left at lower temperatures (SERC).

forsterite and kyanite to spinel and pyrope
5Mg2SiO4 + 4Al2OSiO4 ⇌ MgAl2O4 + 3Mg3Al2 (SiO4)3
Increasing temperature favours the forward reaction (SERC).

forsterite, kyanite and quartz to cordierite
Mg2SiO4 + 2Al2OSiO4 + 2SiO2 ⇌ Mg2Al4Si5O18
At 6 kbar pressure the equilibrium temperature is about 400oC (greenschist facies) (SERC).

grossular and kyanite to anorthite and corundum
Ca3Al2(SiO4)3 + 3Al2OSiO4 ⇌ 3CaAl2Si2O8 + Al2O3
The equilibrium temperature for this reaction at 10 kbar pressure is about 540oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

grossular, kyanite and quartz to anorthite
Ca3Al2(SiO4)3 + 2Al2OSiO4 + SiO2 ⇌ 3CaAl2Si2O8
The equilibrium temperature for this reaction at 10 kbar pressure is about 510o (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

kaolinite to kyanite, pyrophyllite and H2O
3Al2Si2O5(OH)4 ⇌ 2Al2OSiO4 + Al2Si4O10(OH)2 + 5H2O
At 5 kbar pressure the equilibrium temperature for the reaction is about 375oC (greenschist facies), with the equilibrium to the right at higher temperatures and to the left at lower temperatures (SERC, AM61.699-709).

kaolinite and diaspore to kyanite and H2O
Al2Si2O5(OH)4 + 2AlO(OH) ⇌ 2Al2OSiO4 + 3H2O
At 5 kbar pressure the equilibrium temperature for the reaction is about 370oC (greenschist facies), with the equilibrium to the right at higher temperatures and to the left at lower temperatures (SERC, AM61.699-709).

kyanite and enstatite to cordierite and pyrope
6Al2OSiO4 + 5Mg2Si2O6 ⇌ 2Mg2Al4Si5O18 + 2Mg3Al2(SiO4)3
Increasing temperature favours the forward reaction (SERC).

kyanite and enstatite to cordierite and corundum
3Al2O(SiO4) + Mg2Si2O6 ⇌ Mg2Al4Si5O18 + Al2O3
The equilibrium temperature for this reaction at 6 kbar pressure is about 520oC (amphibolite facies), with equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

kyanite and enstatite to quartz and pyrope
2Al2O(SiO4) + 3Mg2Si2O6 ⇌ 2SiO2 + 2Mg3Al2(SiO4)3
The equilibrium temperature for this reaction at 14 kbar pressure is about 950oC (granulite facies), with equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC).

kyanite and forsterite to enstatite and spinel
2Al2OSiO4 + 4Mg2SiO4 ⇌ 3Mg2Si2O6 + 2MgAl2O4
Increasing temperature favours the forward reaction (SERC).

kyanite, forsterite and cordierite to pyrope
2Al2OSiO4 + 5Mg2SiO4 + Mg2Al4Si5O18 ⇌ 4Mg3Al2(SiO4)3
Increasing pressure favours the forward reaction (SERC).

kyanite and pyrope to cordierite and spinel
2Al2OSiO4 + Mg3Al2(SiO4)3 ⇌ Mg2Al4Si5O18 + MgAl2O4
Increasing temperature favours the forward reaction (SERC).

kyanite and zoisite to anorthite, corundum and H2O
2Al2O(SiO4) + 2Ca2Al3[Si2O7][SiO4]O(OH) ⇌ 4CaAl2Si2O8 + Al2O3 + H2O
The equilibrium temperature for this reaction at 5 kbar pressure is 480oC (greenschist facies), and at 10 kbar it is about 720oC (amphibolite facies). The equilibrium is to the right at higher temperatures, and to the left at lower temperatures (SERC, AM61.699-709).

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).

kyanite, zoisite and diaspore to margarite
Al2OSiO4 + Ca2Al3[Si2O7][SiO4]O(OH) + 3AlO(OH) ⇌ 2CaAl2(Al2Si2O10)(OH)2
Increasing temperature favours the forward reaction (SERC)

kyanite, zoisite and quartz to anorthite and H2O
Al2OSiO4 + 2Ca2Al3[Si2O7][SiO4]O(OH) + SiO2 ⇌ 4Al2OSiO4 + H2O
Increasing temperature favours the forward reaction (SERC)

lawsonite to zoisite, kyanite, quartz and H2O
4CaAl2(Si2O7)(OH)2.H2 ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + Al2OSiO4 + SiO2 + 7H2O
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 corundum to zoisite, kyanite and H2O
4CaAl2(Si2O7)(OH)2.H2 + Al2O3 ⇌ 2Ca2Al3[Si2O7][SiO4}O(OH) + 2Al2OSiO4 + 7H2O
The equilibrium temperature for this reaction at 15 kbar pressure is about 570oC (eclogite 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, 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).

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, 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 (AM61.699-709).

paragonite and quartz to albite, kyanite and H2O
NaAl2(Si3Al)O10(OH)2 + SiO2 ⇌ Na(AlSi3O8) + Al2OSiO4 + H2O
Increasing temperature favours the forward reaction (AM61.699-709).

pyrophyllite to kyanite, quartz and H2O
Al2Si2O10(OH)2 ⇌ Al2OSiO4 + 3SiO2 + H2O
At 9 kbar pressure the equilibrium temperature is about 425oC (greenschist facies) (AM61.699-709).

pyrophyllite and diaspore to kyanite and H2O
Al2Si4O10(OH)2 + 6AlO(OH) ⇌ 4Al2OSiO4 + 4H2O
(JVW p 553
This reacton is a higher pressure reaction, occurring above about 1.9 kbar. Increasing temperature favours the forward reaction. At 9 kbar pressure the equilibrium temperature is about 380oC (greenschist facies) (SERC, AM61.699-709).

quartz, kyanite and forsterite to pyrope
SiO2 + 2Al2OSiO4 + 3Mg2SiO4 ⇌ 2Mg3Al2(SiO4)3
Increasing temperature favours the forward reaction (SERC).

quartz, pyrope and kyanite to cordierite
5SiO2 + 2Mg3Al2(SiO4)3 + 4Al2OSiO4 ⇌ 3Mg2Al4Si5O18
Increasing temperature favours the forward reaction (SERC).

spinel, kyanite and enstatite to pyrope
2MgAl2O4 + 2Al2OSiO4 + 5Mg2Si2O6 ⇌ 4Mg3Al2(SiO4)3
Increasing temperature favours the forward reaction (SERC).

talc and kyanite to cordierite, corundum and H2O
2Mg3Si4O10(OH)2 + 7Al2OSiO4 ⇌ 3Mg2Al4Si5O18 + Al2O3 + 2H2O
(DHZ 2A p635)

zoisite and kyanite to margarite and anorthite
2Ca2Al3[Si2O7][SiO4]O(OH) + 2Al2OSiO4 ⇌ CaAl2(Al2Si2O10)(OH)2 + 3Al2OSiO4
Increasing temperature favours the forward reaction (SERC)

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, kyanite and quartz to anorthite and H2O
2Ca2Al3[Si2O7][SiO4]O(OH) + Al2OSiO4 + SiO2 ⇌ 4Ca(Al2Si2O8) + H2O
The equilibrium temperature for this reaction at 10 kbar pressure is about 690oC (amphibolite facies), with the equilibrium to the right at higher temperatures, and to the left at lower temperatures (SERC, AM61.699-709).

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