Albite

Albites
Albites
	Albite from Crete;
General
Category	plagioclase, feldspar, tectosilicate
Formula; (repeating unit)	NaAlSi; 3O; 8 or Na; 1.0–0.9Ca; 0.0–0.1Al; 1.0–1.1Si; 3.0–2.9O; 8
IMA symbol	Ab
Strunz classification	9.FA.35
Crystal system	Triclinic
Crystal class	Pinacoidal (1); (same H-M symbol);
Space group	C1
Unit cell	a = 8.16, b = 12.87; c = 7.11 [Å]; α = 93.45°; β = 116.4°, γ = 90.28°; Z = 4;
Identification
Color	White to gray, blueish, greenish, reddish; may be chatoyant
Crystal habit	Crystals commonly tabular, divergent aggregates, granular, cleavable massive
Twinning	Common giving polysynthetic striae on {001} or {010} also contact, simple and multiple
Cleavage	Perfect on {001}, very good on {010}, imperfect on {110}
Fracture	Uneven to conchoidal
Tenacity	Brittle
Mohs scale hardness	6–6.5
Luster	Vitreous, typically pearly on cleavages
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.60–2.65
Optical properties	Biaxial (+)
Refractive index	nα = 1.528–1.533; nβ = 1.532–1.537; nγ = 1.538–1.542;
Birefringence	δ = 0.010
2V angle	85–90° (low); 52–54° (high)
Dispersion	r < v weak
Melting point	1,100–1,120 °C (2,010–2,050 °F)
Other characteristics	Low- and high-temperature structural modifications are recognized
References

Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula Na Al Si
₃O
₈. It is a tectosilicate. Its color is usually pure white, hence its name from Latin, albus.^[5] It is a common constituent in felsic rocks.

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Handbook of Mineralogy
^ Mindat.org
^ Webmineral data
^ One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Albite". Encyclopædia Britannica (11th ed.). Cambridge University Press.

[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

[Handbook-2] Handbook of Mineralogy

[Mindat-3] Mindat.org

[Webmin-4] Webmineral data

[5] One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Albite". Encyclopædia Britannica (11th ed.). Cambridge University Press.

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Albites
Albite from Crete
General
Category	plagioclase, feldspar, tectosilicate
Formula (repeating unit)	NaAlSi ₃O ₈ or Na _1.0–0.9Ca _0.0–0.1Al _1.0–1.1Si _3.0–2.9O ₈
IMA symbol	Ab^[1]
Strunz classification	9.FA.35
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	C1
Unit cell	a = 8.16, b = 12.87 c = 7.11 [Å]; α = 93.45° β = 116.4°, γ = 90.28°; Z = 4
Identification
Color	White to gray, blueish, greenish, reddish; may be chatoyant
Crystal habit	Crystals commonly tabular, divergent aggregates, granular, cleavable massive
Twinning	Common giving polysynthetic striae on {001} or {010} also contact, simple and multiple
Cleavage	Perfect on {001}, very good on {010}, imperfect on {110}
Fracture	Uneven to conchoidal
Tenacity	Brittle
Mohs scale hardness	6–6.5
Luster	Vitreous, typically pearly on cleavages
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.60–2.65
Optical properties	Biaxial (+)
Refractive index	n_α = 1.528–1.533 n_β = 1.532–1.537 n_γ = 1.538–1.542
Birefringence	δ = 0.010
2V angle	85–90° (low); 52–54° (high)
Dispersion	r < v weak
Melting point	1,100–1,120 °C (2,010–2,050 °F)
Other characteristics	Low- and high-temperature structural modifications are recognized
References	^[2]^[3]^[4]