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
Strunz classification| 9.DE.15
Dana classification| 66.1.3a.12
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
|re|er}}| 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| [1][2][3][4][5]

Pargasite or pargasitic hornblende 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.[7]

It is used as a gemstone.[8][9]

## See also

* Anyolite

## References

1. ↑ Mineralienatlas
2. ↑ 2.0 2.1 "Pargasite" (pdf). Handbook of Mineralogy. Mineralogical Society of America. http://www.handbookofmineralogy.org/pdfs/pargasite.pdf. Retrieved 2012-12-17.
3. ↑ "IMA Master List". http://pubsites.uws.edu.au/ima-cnmnc/.
4. ↑ "Pargasite". mindat.org. http://www.mindat.org/min-3119.html.
5. ↑ 5.0 5.1 "Pargasite Mineral Data". webmineral.com. http://webmineral.com/data/Pargasite.shtml. (Java plugin required)
6. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
7. ↑ 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. doi:10.1038/nature09369. PMID 20865000. Bibcode: 2010Natur.467..448G.
8. ↑ Dedeyne, Roger; Quintens, Evo (2007). Tables of gemstone identification (1st ed.). Gent, Belgium: Glirico. p. 169. ISBN 9789078768012. https://books.google.com/books?id=wnEAcCPBVOsC&q=Tables+of+Gemstone+Identification+By+Roger+Dedeyne,+Ivo+Quintens,+p.169&pg=PA5. Retrieved 5 November 2020.
9. ↑ "Amethyst Crystals and Meaning Healing Properties" (in en-US). 2022-07-11. https://nacrystal.com/amethyst-meaning-and-healing-properties/.

Spinel and pargasite in marble, Luc Yen District, Vietnam. Specimen size: 4.5 × 3.5 × 3.5 cm.

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