Lawsonite

sorosilicate

laumontite

Formula: CaAl2(Si2O7)(OH)2.H2O
Sorosilicate (Si2O7 groups)
Specific gravity: 3.1
Hardness: 7½
Streak: White
Colour: Blue, white
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Environments:

Metamorphic environments

Lawsonite is a common constituent of gneiss and schist formed under low temperature and high pressure. It is a typical mineral of glaucophane schist, associated with chlorite, epidote, titanite, glaucophane, garnet and quartz.
Lawsonite also may be found in gneiss.

It is a mineral of the prehnite-pumpellyite, greenschist, blueschist and eclogite facies.

Alteration

anorthite, albite and H2O to jadeite, lawsonite and quartz
CaAl2 Si2O8 + NaAlSi3O8 + 2H2O → NaAlSi2O6 + CaAl2(Si2O7)(OH)2.H2O + SiO2
(DHZ 2A p475)

grossular and lawsonite to zoisite, prehnite and H2O
Ca3Al2(SiO43 + 3CaAl2(Si2O7)(OH)2.H2O ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + Ca2Al(Si3Al)O10(OH)2 +10H2O
Increasing temperature favours the forward reaction (SERC)

laumontite to lawsonite, quartz and H2O
CaAl2Si4O12.4H2O→ CaAl2(Si2O7)(OH)2.H2O + 2SiO2 + 2H2O
In subduction zones, as the pressure rises to above about 1.5 kbar, laumontite alters to lawsonite according to the above reaction (KB p4).

lawsonite to margarite, zoisite, 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, 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 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 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 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 grossular to zoisite, quartz and H2O
5CaAl2(Si2O7)(OH)2.H2O + Ca3Al2(SiO43 ⇌ 4Ca2Al3[Si2O7][SiO4]O(OH) + SiO2 + 18H2O
Increasing temperature favours the forward reaction (SERC)

lawsonite, grossular and quartz to prehnite
CaAl2(Si2O7)(OH)2.H2O + Ca3Al2(SiO43 + SiO2 ⇌ 2Ca2Al(Si3Al)O10(OH)2
Increasing temperature favours the forward reaction (SERC)

lawsonite and jadeite to clinozoisite, paragonite, quartz and H2O
4CaAl2(Si2O7)(OH)2.H2 + NaAlSi2O6 ⇌ 2Ca2Al3[Si2o7][SiO4]O(OH) + NaAl2(Si3Al)O10(OH)2 + SiO2 +6H2
(DHZ 2A p477)

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).

lawsonite and quartz to wairakite
CaAl2(Si2O7(OH)2.H2O + 2SiO2 ⇌ Ca(Si4Al2)O10.2H2O
Increasing temperature favours the forward reaction (AM61.699-709).

prehnite and lawsonite to zoisite, quartz and H2O
Ca2Al(Si3Al)O10(OH)2 + 2CaAl2(Si2O7)(OH)2.H2O ⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) + SiO2 + 8H2O
Increasing temperature favours the forward reaction (SERC)

Back to Minerals