Albite

tectosilicate

andesine

Formula: Na(AlSi3O8)
Tectosilicate (framework silicate)
albite is a plagioclase feldspar.
Andesine is a variety of albite rarely found except as grains in andesite.
Cleavelandite is a platy variety of albite, generally found in pegmatites.
Oligoclase is a variety of albite belonging to the amphibolite facies.
Specific gravity: 2.60 to 2.65
Hardness: 6 to 6½
Streak: White
Colour: Colourless, white
Melting point (albite): About 1,100oC at atmospheric pressure
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Environments (albite):

Pegmatites
Carbonatites
Metamorphic environments

Albite is a primary mineral crystallising at the low temperature end of the continuous arm of the Bowen reaction series. It is a plagioclase feldspar found in pegmatites and carbonatites. It is a secondary mineral in contact and regional metamorphic environments.
Intrusion-related albite is found in the core of some porphyry (rock with coarse phenocrysts in a finer groundmass) systems associated with alkaline or felsic intrusions (AofA).
Albite is a common but not essential constituent of granite and granite pegmatites.
It also may be found in metamorphosed quartz sandstone, rhyolite, trachyte, hornfels, phyllite and schist.
In nepheline syenite pegmatites and carbonatites albite is associated with aegirine and nepheline.
In rhyolite and trachyte it may replace earlier microcline.
Albite is characteristic of the zeolite and albite-epidote-hornfels facies. It is also a mineral of the prehnite-pumpellyite, greenschist, amphibolite and blueschist facies.

Environments (andesine):

Plutonic igneous environments
Metamorphic environments

Andesine is widespread in igneous rocks of intermediate silica content, such as syenite and andesite. It is characteristic of the amphibolite and granulite facies. It is rarely found except as grains in andesite (where it may be associated with augite) and diorite.

Environments (oligoclase):

Plutonic igneous environments
Pegmatites
Metamorphic environments

Oligoclase is a common but not essential constituent of granodiorite.
It also may be found in granite, monzonite, gabbro, anorthosite and in gneiss with biotite and hornblende.
It is a mineral of the amphibolite and granulite facies.
Andesine and oligoclase occur towards the higher temperature range of albite and its varieties (JVW p143 & KB p209).

Albite localities:

At the Sapo mine, Minas Gerais, Brazil, albite is abundant in the pegmatite, associated with microcline, especially in large, quartz-bearing cavities. It is mostly of the cleavelandite variety, often intergrown with muscovite with hollow voids whhich may be moulds of dissolved spodumene crystals (Min Rec 40.4.278).

At the Little Gem amethyst mine, Jefferson county, Montana, USA, albite occurs intergrown with microcline (R&M 93.6.512)

Alteration

aegirine, epidote and CO2 to albite, hematite, quartz, calcite and H2O
4NaFe3+Si2O6 + 2Ca2(Al2Fe3+ [Si2O7](SiO4)O(OH) + 4CO2 → 4Na(AlSi3O8) + 3Fe2O3 + 2SiO2 + 4CaCO3 + H2O (DHZ 2A p511)

aenigmatite, anorthite and O2 to hedenbergite, albite, ilmenite and magnetite
½Na4[Fe2+10Ti2]O4[Si12O36] + CaAl2Si2O8 + ½O2 = CaFe2+Si2O6 + 2NaAlSi3O8 + Fe2+Ti4+O3 + Fe2+Fe3+2O4 (DHZ 2A p651)

albite to nepheline and quartz
Na(AlSi3O8) ⇌ NaAlSiO4 + 2SiO2

albite and NaCl (aqueous) to sodalite and silica
6Na(AlSi3O8) + 2NaCl → 2Na4(Si3Al3)O12Cl + 12SiO2 (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.613.9474&rep=rep1&type=pdf)

albite, chlorite and calcite to Ca, Mg-rich jadeite, Al-rich glaucophane, quartz, CO2 and H2O
8Na(AlSi3O8) + (Mg4.0Fe2.0)(AlSi3O10)(OH)8 + CaCO3 → 5(Na0.8Ca0.2)(Mg0.2Al0.8Si2)6 + 2Na2(Mg3Al2)(Al0.5Si7.5)O22(OH)2 + 2SiO2 + CO2 + 2H2O
In low to intermediate metamorphism jadeite-glaucophane assemblages may arise from reactions such as the one above (DHZ 2A p475).

albite, diopside and magnetite to aegirine, Si2O6, garnet and quartz
2Na(AlSi3O8) + CaMgSi2O6 + Fe2+Fe3+2O4 ⇌ 2NaFe3+Si2O6 + Si2O6 + CaMgFe2+Al2(SiO4)3 + SiO2
This reaction may occur in blueschist facies rocks in Japan (DHZ 2A p512).

albite and montmorillonite to Ca, Mg-rich jadeite, Al-rich glaucophane, quartz and H2O
8Na(AlSi3O8) + 2Ca0.5(Mg3.5Al0.5)Si8O20(OH)4.nH2O → 5(Na0.8Ca0.2)(Mg0.2Al0.8Si2)6 + 2Na2(Mg3Al2)(Al0.5Si7.5)O22(OH)2 + 15SiO2 + 6H2O
This reaction occurs in low to intermediate metatmorphism (DHZ 2A p 475).

amphibole, clinozoisite, chlorite, albite, ilmenite and quartz to garnet, omphacite, rutile and H2O
NaCa2(Fe2Mg3)(AlSi7)O22(OH)2 + 2Ca2Al3[Si2o7][SiO4]O(OH) + Mg5Al(AlSi3O10)(OH)8 + 3NaAlSi3O8 + 4Fe2+Ti4+O3 + 3SiO2 → 2(CaMg2Fe3)Al4(SiO4)6 + 4NaCaMgAl(Si2O6)2 + 4TiO2 + 6H2O
In low-grade rocks relatively poor in calcite the garnet-omphacite association may be developed by the above reaction (DHZ 2A p453).

analcime and quartz to albite and H2O
Na(AlSi2O6).H2O + SiO2 ⇌ Na(AlSi3O8) + H2O (JVW p144)

anorthite, albite and H2O to jadeite, lawsonite and quartz
CaAl2 Si2O8 + NaAlSi3O8 + 2H2O → NaAlSi2O6 + CaAl2(Si2O7)(OH)2.H2 + SiO2 (DHZ 2A p475)

antigorite and albite to glaucophane and H2O
Mg3Si2O5(OH)4 + 2Na(AlSi3O8) → ☐Na2(Mg3Al2)Si8O22(OH)2 + H2O
This is a metamorphic reaction (DHZ 3 p156).

augite, albite, pyroxene, anorthite and ilmenite to omphacite, garnet, quartz and rutile
2MgFe2+Si2O6 + Na(AlSi3O8) + Ca2Mg2Fe2+Fe3+AlSi5O18 + 2Ca(Al2Si2O8) + 2Fe2+Ti4+O3 → NaCa2MgFe2+Al(Si2O6)3 + (Ca2Mg3Fe2+4)(Fe3+Al5)(SiO4)9 + SiO2 + 2TiO2
This reaction occurs at high temperature and pressure (DHZ 2A p449).

chlorite (clinichlore), actinolite and albite to glaucophane, iron-poor epidote, SiO2 and H2O
9Mg5Al(AlSi3O10)(OH)8 + 6☐Ca2Mg5Si8O22(OH)2 + 50Na(AlSi3O8) → 25☐Na2(Mg3Al2)Si8O22(OH)2 + 6Ca2Al3[Si2O7][SiO4]O(OH) + 7SiO2 + 14H2O
This is a metamorphic reaction (DHZ 3 p156).

diopside and albite to omphacite and quartz
CaMgSi2O6 + xNaAlSi3O8 ⇌ CaMgSi2O6.xNaAlSi2O6 + SiO2 (DHZ 2A p453).

enstatite-ferrosilite, diopside-hedenbergite, albite, anorthite and H2O to amphibole and quartz
+ Ca(Al2Si2O8) + H2O ⇌ NaCa2(Mg,Fe)4Al(Al2O6)O22(OH)2 + 4SiO2
This reaction represents metamorphic reactions between the granulite and amphibolite facies (DHZ 2A p139)

enstatite-ferrosilite, diopside-hedenbergite, albite, anorthite and H2O to amphibole and quartz
3(Mg,Fe2+)SiO3 + Ca(Mg,Fe2+)Si2O6 + NaAlSi3O8 + Ca(Al2Si2O8) + H2O ⇌ NaCa2(Mg,Fe)4Al(Al2O6)O22(OH)2 + 4SiO2
This reaction represents metamorphic reactions between the granulite and amphibolite facies (DHZ 2A p139).

jadeite to nepheline and albite
2NaAlSi2O6 ⇌ NaAlSiO4 + NaAlSi3O8
At 20 kbar pressure the equilibrium temperature is about 1,000oC (eclogite facies), with equilibrium to the right at higher temperatures and to the left at lower temperatures (Minsoc Amer sp pap 2, 151-161 (1969)).

jadeite and quartz to albite
NaAlSi2O6 + SiO2 ⇌ NaAlSi3O8
The equilibrium temperature for this reaction at 10 kbar pressure is about 400oC (blueschist facies), and at 26 kbar the equilibrium temperature is 1,000oC (eclogite facies). For any given pressure the equilibrium is to the right at higher temperatures, and to the left at lower temperatures, and for any given temperature the equilibrium is to the left at higher pressures and to the right at lower pressures.

labradorite (variety of anorthite), albite, forsterite and diopside to omphacite, garnet and quartz
3CaAl2Si2O8 + 2Na(AlSi3O8) + 3Mg2SiO4 + nCaMgSi2O6 → (2NaAlSi2O6 + nCaMgSi2O6) + 3(CaMg2)Al2(SiO4)3 + 2SiO2
This reaction occurs at high temperature and pressure (DHZ 2A p449).

nepheline and diopside to åkermanite, forsterite and albite
3NaAlSiO4 + 8CaMgSi2O6 ⇌ 4Ca2MgSi2O7 + 2Mg2SiO4 + 3NaAlSi3O8
This reaction is in equilibrium at about 1180oC, with lower temperatures favouring the forward reaction (DHZ 4 p251).

paragonite and quartz to albite and andalusite and H2O
NaAl2(Si3Al)O10(OH)2 + SiO2 ⇌ Na(AlSi3O8) + Al2OSiO4 + H2O
Increasing temperature favours the forward reaction (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).

spodumene and Na+ to eucryptite, albite and Li+
2LiAlSi2O6 + Na+ → LiAlSiO4 + NaAlSi3O8 + Li+
Whether spodumene breaks down into albite or into eucryptite and albite depends largely on the presence or absence of quartz (AM 67.97-113).

spodumene, quartz and Na+ to albite and Li+
LiAlSi2O6 + SiO2 + Na+ → NaAlSi3O8 + Li+
Whether spodumene breaks down into albite or into eucryptite and albite depends largely on the presence or absence of quartz (AM 67.97-113).

magnesium-rich tremolite, tschermakite and albite to pargasite and quartz
☐Ca2Mg5Si8O22(OH)2 + ☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2 + 2Na(AlSi3O8) ⇌ 2NaCa2(Mg4Al)(Si6Al2)O22(OH)2 + 8SiO2
(AM 92.4.491)

Common impurities: Ca,K,Mg

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