pargasite

{{short description|Amphibole, double chain inosilicate mineral}}

{{Infobox mineral

| name = Pargasite

| category = Inosilicates

| boxwidth =

| boxbgcolor =

| image = Pargasite-ww49d.jpg

| caption = Single crystal of pargasite, 1.5 cm long, on a matrix of white marble from Hunza Valley, Pakistan

| formula = NaCa₂(Mg₄Al)(Si₆Al₂)O₂₂(OH)₂

| IMAsymbol = Prg{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}

| strunz = 9.DE.15

| dana = 66.1.3a.12

| molweight =

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = C2/m

| color = Bluish green, grayish black, light brown

| habit = Stout prismatic to tabular

| twinning = Simple and lamellar – common

| cleavage = {110} perfect

| fracture = Splintery

| mohs = 5–6

| luster = Vitreous

| refractive = nα = 1.630 nβ = 1.640 nγ = 1.650

| opticalprop = Biaxial (−)

| birefringence = δ = 0.020 max.

| pleochroism =

| streak =

| gravity = 3.04–3.17

| density =

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = Translucent, will transmit light on thin edges.

| other =

| references = [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Pargasite Mineralienatlas]

{{cite book |chapter-url=http://www.handbookofmineralogy.org/pdfs/pargasite.pdf

|url=http://www.handbookofmineralogy.org |title=Handbook of Mineralogy

|chapter=Pargasite |format=pdf

|publisher=Mineralogical Society of America |access-date=2012-12-17

}}{{Cite web |url=http://pubsites.uws.edu.au/ima-cnmnc/ |title=IMA Master List |access-date=2014-05-12 |archive-date=2015-01-05 |archive-url=https://web.archive.org/web/20150105154315/http://pubsites.uws.edu.au/ima-cnmnc/ |url-status=dead }}

{{cite web |url=http://www.mindat.org/min-3119.html

|title=Pargasite |publisher=mindat.org

|access-date=2012-12-17 }}

{{cite web |url=http://webmineral.com/data/Pargasite.shtml

|title=Pargasite Mineral Data |publisher=webmineral.com

|access-date=2012-12-17

}} {{link note |note=Java plugin required |date=December 2012}}

}}

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.

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.

Pargasite is the main water-storage site in the uppermost mantle; however, it becomes unstable at depths greater than {{convert|90|km|abbr=on}}. This has significant consequences for the water storage capacity, and the solidus temperature of the lherzolite of the upper mantle.

{{cite journal

|last1=Green

|first1=D H

|last2=Hibberson

|first2=W O

|last3=Kovacs

|first3=Istvan

|last4=Rosenthal

|first4=A

|title=Water and its influence on the lithosphere–asthenosphere boundary

|journal=Nature

|date=23 September 2010

|volume=467

|issue=7314

|pages=448–451

|doi=10.1038/nature09369

|pmid=20865000

|bibcode=2010Natur.467..448G

|s2cid=4393352

}} {{subscription required |date=December 2012}}

It is used as a gemstone.{{cite book |last1=Dedeyne |first1=Roger |last2=Quintens |first2=Evo |title=Tables of gemstone identification |date=2007 |publisher=Glirico |location=Gent, Belgium |isbn=9789078768012 |page=169 |edition=1st |url=https://books.google.com/books?id=wnEAcCPBVOsC&q=Tables+of+Gemstone+Identification+By+Roger+Dedeyne,+Ivo+Quintens,+p.169&pg=PA5 |access-date=5 November 2020}}{{Cite web |date=2022-07-11 |title=Amethyst Crystals and Meaning Healing Properties |url=https://nacrystal.com/amethyst-meaning-and-healing-properties/ |access-date=2023-02-10 |website=nacrystal.com |language=en-US}}