Pargasite

Pargasite
Pargasite
	Single crystal of pargasite, 1.5 cm long, on a matrix of white marble from Hunza Valley, Pakistan
General
Category	Inosilicates
Formula; (repeating unit)	NaCa2(Mg4Al)(Si6Al2)O22(OH)2
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) ; (same H-M symbol)
Space group	C2/m
Identification
Color	Bluish green, grayish black, light brown
Crystal habit	Stout prismatic to tabular
Twinning	Simple and lamellar - common
Cleavage	{110} perfect
Fracture	Splintery
Mohs scale hardness	5–6
Luster	Vitreous
Diaphaneity	Translucent, will transmit light on thin edges.
Specific gravity	3.04–3.17
Optical properties	Biaxial (-)
Refractive index	nα = 1.630 nβ = 1.640 nγ = 1.650
Birefringence	δ = 0.020 max.
References

Pargasite is a complex inosilicate mineral of the amphibole group with formula NaCa₂(Mg₄Al)(Si₆Al₂)O₂₂(OH)₂.

It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality.^[5]

It occurs in high temperature regional metamorphic rocks and in the skarns within contact aureoles around igneous intrusions. It also occurs in andesite volcanic rocks and altered ultramafic rocks.^[2]

Pargasite is the main water-storage site in the uppermost mantle, however it becomes unstable at depths greater than 90 km (56 mi). This has significant consequences for the water storage capacity, and the solidus temperature of the lherzolite of the upper mantle.^[6]

It is used as a gemstone.^[7]

References[]

^ Mineralienatlas
^ Jump up to: ^a ^b "Pargasite" (PDF). Handbook of Mineralogy (pdf). Mineralogical Society of America. Retrieved 2012-12-17.
^ "IMA Master List". Archived from the original on 2015-01-05. Retrieved 2014-05-12.
^ "Pargasite". mindat.org. Retrieved 2012-12-17.
^ Jump up to: ^a ^b "Pargasite Mineral Data". webmineral.com. Retrieved 2012-12-17. (Java plugin required)
^ Green, D H; Hibberson, W O; Kovacs, Istvan; Rosenthal, A (23 September 2010). "Water and its influence on the lithosphere–asthenosphere boundary". Nature. 467 (7314): 448–451. Bibcode:2010Natur.467..448G. doi:10.1038/nature09369. PMID 20865000. (subscription required)
^ Dedeyne, Roger; Quintens, Evo (2007). Tables of gemstone identification (1st ed.). Gent, Belgium: Glirico. p. 169. ISBN 9789078768012. Retrieved 5 November 2020.

Spinel and Pargasite on Marble, Luc Yen District, Vietnam. Specimen size: 4.5 x 3.5 x 3.5 cm.

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[1] Mineralienatlas

[Handbook-2] Jump up to: ^a ^b "Pargasite" (PDF). Handbook of Mineralogy (pdf). Mineralogical Society of America. Retrieved 2012-12-17.

[3] "IMA Master List". Archived from the original on 2015-01-05. Retrieved 2014-05-12.

[Mindat-4] "Pargasite". mindat.org. Retrieved 2012-12-17.

[Webmineral-5] Jump up to: ^a ^b "Pargasite Mineral Data". webmineral.com. Retrieved 2012-12-17. (Java plugin required)

[6] Green, D H; Hibberson, W O; Kovacs, Istvan; Rosenthal, A (23 September 2010). "Water and its influence on the lithosphere–asthenosphere boundary". Nature. 467 (7314): 448–451. Bibcode:2010Natur.467..448G. doi:10.1038/nature09369. PMID 20865000. (subscription required)

[7] Dedeyne, Roger; Quintens, Evo (2007). Tables of gemstone identification (1st ed.). Gent, Belgium: Glirico. p. 169. ISBN 9789078768012. Retrieved 5 November 2020.

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Pargasite

See also[]

References[]