View source for Lazurite

{{Short description|Alumino-silicate mineral whose blue colour is due to a sulfide species and not copper}}
{{Distinguish|Azurite|Lazulite}}
{{Other uses|Azure spar}}
{{Infobox mineral
| name        = Lazurite
| category    = [[Tectosilicate]] [[minerals]], [[feldspathoid]] [[Mineral group|group]], [[sodalite]] group
| boxwidth    = 
| boxbgcolor  = 
| image       = Lazurite.jpg
| imagesize   = 
| caption     = Lazurite, Ladjuar Medam (Lajur Madan; Lapis-lazuli Mine), Sar-e-Sang District, Koksha Valley (Kokscha; Kokcha), Badakhshan (Badakshan; Badahsan) Province, Afghanistan
| formula     = {{chem2|(Na,Ca)8[(S,Cl,SO4,OH)2{{!}}(Al6Si6O24)]}}
| IMAsymbol   = Lzr<ref>{{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}}</ref>
| strunz      = 9.FB.10
| system      = [[Cubic (crystal system)|Isometric]]
| class       = Hextetrahedral ({{overline|4}}3m) <br/>[[H-M symbol]]: ({{overline|4}} 3m)
| symmetry    = ''P''{{overline|4}}3n
| unit cell   = a = 9.09&nbsp;[[Ångstrom|Å]]; Z&nbsp;=&nbsp;2
| color       = Deep blue, azure, violet-blue, greenish blue
| habit       = Crystals occur as dodecahedra, or rarely cubes; granular, disseminated, or massive
| twinning    = 
| cleavage    = Imperfect on {110}
| fracture    = Uneven
| tenacity    = Brittle
| mohs        = 5–5.5
| luster      = Vitreous
| refractive  = 1.502–1.522
| opticalprop = Isotropic; anomalously anisotropic
| birefringence = 
| pleochroism = 
| streak      = 
| gravity     = 2.38–2.45
| density     = 
| melt        = 
| fusibility  = 3.5
| diagnostic  = 
| solubility  = Soluble in [[Hydrochloric acid|HCl]]
| diaphaneity = Translucent to opaque
| other       = 
| references  =<ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/lazurite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-2357.html Mindat with location data]</ref><ref name=Webmin>[http://webmineral.com/data/Lazurite.shtml Webmineral data]</ref><ref name=Klein>Hurlbut, Cornelius S. and Klein, Cornelis, 1985, ''Manual of Mineralogy'', 20th ed., Wiley, p. 459 {{ISBN|0-471-80580-7}}</ref><ref>{{Cite web |url=http://www.handbookofmineralogy.com/pdfs/lazurite.pdf |title=Mineralogical Society of America |access-date=2011-03-08 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303180014/http://www.handbookofmineralogy.com/pdfs/lazurite.pdf |url-status=dead }}</ref>
}}

'''Lazurite''', old name ''[[Azure spar]]''<ref name="kriv">''Krivovichev V. G.'' Mineralogical glossary. Scientific editor [[:uk:Булах Андрій Глібович|A. G. Bulakh]]. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)''</ref>{{rp|14}} is a [[Silicate minerals|tectosilicate]] mineral with [[sulfate]], [[sulfur]] and [[chloride]] with formula {{chem2|(Na,Ca)8[(S,Cl,SO4,OH)2{{!}}(Al6Si6O24)]}}. It is a [[feldspathoid]] and a member of the [[sodalite]] group. Lazurite crystallizes in the [[Cubic (crystal system)|isometric]] system although well‐formed crystals are rare. It is usually massive and forms the bulk of the gemstone [[lapis lazuli]].

==Mineral==
Lazurite is a deep‐blue to greenish‐blue. The colour is due to the presence of [[Trisulfur#Radical anion|{{chem|S|3|-}}]] anions.<ref name=Sapozhnikov>{{Cite journal |author=Tauson VL, Sapozhnikov AN |year=2003 |title=On the nature of lazurite coloring |journal=Zapiski Vserossijskogo Mineralogicheskogo Obshchestva |volume=132 |issue=5 |pages=102–107 |url=http://rruff.info/rruff_1.0/uploads/ZVMO132N5_102.pdf |language=ru }}</ref> It has a [[Mohs hardness]] of 5.0 to 5.5 and a [[specific gravity]] of 2.4. It is translucent with a [[refractive index]] of 1.50. It is fusible at 3.5 on [[Wolfgang Franz von Kobell]]'s [[fusibility]] scale, and soluble in [[Hydrochloric acid|HCl]]. It commonly contains or is associated with grains of [[pyrite]].

Lazurite is a product of [[contact metamorphism]] of [[limestone]] and is typically associated with [[calcite]], pyrite, [[diopside]], [[humite]], [[forsterite]], [[hauyne]] and [[muscovite]].<ref name=HBM/>

Other blue minerals, such as the [[carbonate]] mineral, [[azurite]], and the [[phosphate]] mineral, [[lazulite]], may be confused with lazurite, but are easily distinguished with careful examination. At one time, lazurite was a synonym for [[azurite]].<ref name=Klein/>

Lazurite was first described in 1890 for an occurrence in the [[Sar-e-Sang]] District, [[Koksha Valley]], [[Badakhshan]] Province, [[Afghanistan]].<ref name=Mindat/> It has been mined for more than 6,000 years in the [[lapis lazuli]] district of Badakhshan. It has been used as a pigment in painting and cloth [[dyeing]] since at least the 6th or 7th century.<ref name=Eastlaugh>{{cite book |last=Eastaugh |first=Nicholas |display-authors=et al |year=2004 |title=The Pigment Compendium: Optical Microscopy of Historical Pigments |place=Oxford |publisher=Elsevier Butterworth-Heinemann |page=219 |isbn=0-7506-4553-9}}</ref> It is also mined at [[Lake Baikal]] in Siberia; [[Vesuvius|Mount Vesuvius]]; [[Burma]]; [[Canada]]; and the [[United States]].<ref name=Eastlaugh/> The name is from the [[Persian language|Persian]] {{Transliteration|fa|lajvard}} for blue.<ref name="VandA">{{cite web | url=https://collections.vam.ac.uk/item/O256542/tile-fragment/ | title=Tile fragment | publisher=Victoria and Albert Museum | access-date=11 January 2020}}</ref>

The most important mineral component of lapis lazuli is lazurite.<ref name="mindatLapisLazuli">{{Cite web|url=https://www.mindat.org/min-2330.html
|title=Lapis lazuli: Mineral information, data and localities.|website=www.mindat.org|access-date=2024-08-30|archive-date=2020-01-29|archive-url=https://web.archive.org/web/20200129083053/https://www.mindat.org/min-2330.html|url-status=live}}</ref> (25% to 40%){{citation needed|date=August 2024}}

== Redefinition ==
Most lapis lazuli gets its blue color from Hauyne and almost none contain "true lazurite".<ref name="mindatLapisLazuli" /> This was changed in 2021, as lazurite was redefined so that it is enough for a quarter (instead of half) of the cages to contain sulfide.<ref>{{cite web |url=https://www.mindat.org/min-2357.html |title=Lazurite |access-date=2024-08-30 |website=mindat.org}}</ref>

== Structure ==
Lazurite and [[hauyne]] seem to have the same structure and both are sulfate-dominant minerals.<ref>{{Cite journal |author1=Moore, T.P. |author2=Woodside, R. W. M. |year=2014 |title=The Sar-e-Sang Lapis Mines |journal=Mineralogical Record |volume=45 |issue=3 |pages=281–336}}</ref> Lazurite is a [[pigment]] (opalescent) and has a bright blue streak (especially as a component of the semiprecious stone [[lapis lazuli]]). Many hauynes have a white or pale blue streak and are translucent. The difference might be a consequence of the [[Redox potential|redox state]] (sulfate to sulfide ratio).<ref name=Sapozhnikov/><ref>{{Cite journal |vauthors=Hettmann K, Wenzel T, Marks M, Markl G |year=2012 |title=The sulfur speciation in S-bearing minerals: New constraints by a combination of electron microprobe analysis and DFT calculations with special reference to sodalite-group minerals |journal=American Mineralogist |volume=97 |issue=10 |pages=1653–1661|doi=10.2138/am.2012.4031 |bibcode=2012AmMin..97.1653H |s2cid=54921328 }}</ref>

==See also==
* {{annotated link|Hauyne}}
* {{annotated link|Ultramarine}}

==References==
<references/>

== External links ==
* {{Commons category-inline| Lazurite}}

{{Gemstones}}
{{Authority control}}

[[Category:Sodalite group]]
[[Category:Sodium minerals]]
[[Category:Calcium minerals]]
[[Category:Aluminium minerals]]
[[Category:Pigments]]
[[Category:Cubic minerals]]
[[Category:Minerals in space group 218]]